Category: Hearing Loss

The process of hearing can be described as a series of events in which the energy of sound is transformed from vibrations in the air captured by structures of the outer ear (e.g. pinna) and further transferred through the ear canal to cause vibration of the tympanic membrane and ossicles of the middle ear, which then become traveling waves in the fluid contained within the cochlea. This leads to stimulation of the inner ear hair cells that, in turn, stimulate spiral ganglion neurons that transfer these signals to the primary auditory cortex, where these impulses are deciphered according to intensity and frequency. This complex combination of mechanosensory and physiological mechanisms involves many distinct types of cells, the function of which are impacted by numerous proteins, including those involved in ion channel activity, signal transduction and transcription. In the last 30 years, pathogenic variants in over 150 genes were found to be linked to hearing loss. Hearing loss affects over 460 million people world-wide, and current treatment approaches, such as hearing aids and cochlear implantations, serve to improve hearing capacity but do not address the underlying genetic cause of hearing loss. Therefore, therapeutic strategies designed to correct the genetic defects causative for hearing loss offer the possibility to treat these patients. In this review, we will discuss genetic causes of hearing loss, novel gene therapeutic strategies to correct hearing loss due to gene defects and some of the preclinical studies in hearing loss animal models as well as the clinical translation of gene therapy approaches to treat hearing loss patients.

Keywords: hearing loss, genetic variants, sequencing, gene therapy, genome editing

Introduction

Genetic diagnosis of hearing loss allows prognostic disease assessment and provides the opportunity for early therapeutic intervention. Identification of genes associated with hearing loss has led to deeper insight into the underlying biology of normal hearing and pathology of hearing loss. Coupled with our increased understanding of genetics and advances in molecular biology techniques, this information has greatly facilitated design of novel medical strategies to treat hereditary hearing loss, such as gene therapy approaches. Indeed, the first clinical trial testing gene therapy in hearing loss patients was initiated and there are several gene transfer modalities available for further evaluation and optimization.

Main text

From genetic causes to novel therapeutics

Hearing is dependent upon the coordinated interaction of several cell types and their responses to mechanical and physiological stimuli. Especially cells of the sensory epithelium, including the inner and outer hair cells (HC) as well as spiral ganglion neurons (SGN) of the inner ear, play key roles in the hearing process (Figure 1). As with other human diseases, genetic aberrations that impact cellular functions can also lead to hearing loss.

Advances in sequencing technologies led to more rapid identification of genetic aberrations linked to hearing loss. Currently, pathogenic variants (PV) in more than 150 genes are known to be associated with hearing loss [42] (http://www.hereditaryhearingloss.org). Introduction of PV genotypes into various animal models has helped to reveal the biological mechanisms through which loss of functional proteins leads to hearing loss and has also led to improved understanding of normal hearing processes (Figure 1). For example, loss of function variants cause disruption of cellular and molecular processes necessary for normal hearing, such as inner ear sensory cell development, control of transmembrane potentials via ion channels, gap junction channels for maintenance of the endocochlear potential, glutamate signaling and alternative gene splicing events.

Identification of PV in hearing loss patients also allows the possibility for personalized medicine approaches such as gene therapy to treat these patients. Knowledge gained from previous experience using gene therapies to treat other human diseases can be exploited to adapt protocols for use in hearing loss patients. Here, some of the most relevant vector technologies available for gene therapy of the inner ear include adenoviral (AdV) vectors, adeno-associated viral (AAV) vectors and lentiviral vectors. Each of these vector systems has unique properties with potential advantages and disadvantages. Importantly, these vector systems are currently used to deliver advanced genome editing tools to correct PV in target cell populations and the relevance of this technology to repair genetic lesions in inner ear cells with the aim to improve hearing is a clinically relevant area to be exploited. In combination with the extensive information acquired from animal models, gene transfer and genomic modification technologies are expected to drive clinical development of novel gene therapy strategies to treat hearing loss patients.

Genetic alterations and clinical consequences

Hereditary hearing loss can be divided into two major subgroups, syndromic – i.e. as a symptom of a superordinate disorder involving further anomalies of the ear and other organ systems – and non-syndromic hearing loss (NSHL), involving only the function of the inner ear. Today more than 400 distinctive syndromes are well-defined, for which hearing loss is a characteristic mandatory or accessory symptom. Many non-distinctive syndromes and multi-systemic disorders comprise hearing loss as well. Approximately 70 % of genetically determined hearing loss is non-syndromic [2]. The by far most common genetic cause for hereditary NSHL are pathogenic variants affecting the gene GJB2, which account for roughly 10-30 % of NSHL [22, 46, 59], reaching over 50% in some ethnic groups [8]. Noteworthy, the majority of NSHL is distributed among more than 100 genes known to be associated with NSHL, and likely more will be identified. Hereditary hearing loss may follow an autosomal recessive (most frequently, about 80 % of NSHL), autosomal dominant, X-linked or mitochondrial inheritance pattern [2].

The underlying molecular changes are variable and comprise substantial numbers of truncating, missense and intronic variants as well as copy number variations (CNVs). While historically the genetic heterogeneity restricted testing to just a few genes, recent studies underline the benefits of comprehensive genetic testing by targeted sequencing panel analysis [45]. Against a background of steadily decreasing costs with continuously improving sequencing coverage as well as increasing reliability in computed CNV detection, it is only a question of time before whole exome sequencing (WES) and soon whole genome sequencing (WGS) will become the preferred method. There is no doubt that the interpretation of a large number of variants remains a major challenge in all of these techniques, as well as the task to handle and appropriately report a multitude of variants of unknown significance (VUS) [34]. The identification of the genetic cause becomes increasingly important regarding personalized prognosis and therapy selection [40]. Regarding the outcome of cochlear implant therapy, recipients with genetic alterations affecting the function of the cochlear sensory organ seem to perform significantly better in terms of speech recognition than patients with PV in genes associated with spiral ganglion neuron function [41].

Thus, all newborns and infants as well as children and young adults with confirmed (syndromic or non-syndromic) hearing loss without strong evidence for an environmental etiology should be seen by a geneticist and offered testing. In adults, a more detailed assessment of the development of hearing loss seems appropriate before recommending genetic counseling, although literature suggests that over 30% of adult onset progressive hearing loss that results in cochlear implantation has a genetic cause [33]. Once a causative PV is identified, genetic testing should be offered to family members at risk. Genetic counseling may also include assessment of recurrence risk for potential offspring [2]. While performing prenatal as well as preimplantation genetic diagnosis is generally feasible, this should be carefully considered with respect to the Deaf culture [42] and according to country-specific legal aspects. Due to the extreme heterogeneity of genetically determined hearing loss that accompanies the complex challenge of variant interpretation, general population-wide prenatal or newborn genetic screening is currently not recommended. However, in the future, screening for at least specific genetic alterations should be considered in addition to physiologic newborn screening [9, 43], with particular regards to targeted and potentially curative therapeutic approaches. Determination of genetic aberrations responsible for a patient´s hearing loss can be used to direct personalized approaches like gene therapy.

Vector options to introduce gene therapeutics into the inner ear

Generally, different concepts are available for gene therapy of hereditary hearing loss. To substitute for the function of a defective gene, an intact copy can be introduced into the relevant cells of the inner ear. Gene suppression, for example through expression of an shRNA that targets the transcript of the mutated gene to prevent its translation, can serve to eliminate dominant-negative effects that may interfere with proper cellular function even if an intact gene copy is provided. Finally, gene correction utilizing gene editing based on designer nuclease systems allows the specific removal of PV, thereby also keeping the natural regulation of gene expression via the physiologic promoter and chromatin environment.

Common to all different gene therapy strategies is the requirement for efficient transfer technologies to equip the target cells with expression units for the intact gene or miRNA, for shRNAs, or for the gene editing components. The complex 3D architecture and defined arrangement of the specific cell types inside the cochlea (see Figure 1) excludes ex-vivo cell manipulation and restricts treatment options to in vivo delivery systems. This is in contrast to other organ systems, such as the hematopoietic system, where stem cells can be extracted and re-infused into the patient upon ex-vivo genetic therapy. Viruses have evolutionarily co-evolved with their hosts and, as such, have developed specialized mechanisms to enter their target species and cell type(s). Therefore, viral vectors appear to be ideal vehicles to deliver genetic information to the cochlea. Furthermore, the different compartments in the cochlea are filled with lymph, which allows for the distribution of injected viral vector throughout the cochlea via this intracochlear fluid, while spread to other organs is theoretically limited to the enclosed organ system of the inner ear.

Several parameters are important for the success of viral-vector-based gene therapy approaches in the cochlea: (1) The vector volume that can be administered is limited. The outer wall of the inner ear is rigid, so that injection of too high vector volumes would increase the pressure and cause hydraulic trauma. Standard injection volumes are 1 µL in mice and are estimated to be 10-30 µL in humans. Thus, high-titer vector preparations are required to allow delivery in a small volume. One advantage for gene therapy application to the inner ear is that the total number of cells present in the cochlea is low as compared to other gene-therapy-relevant organ systems, so that a comparably low number of vector particles should suffice to achieve clinical benefit. (2) The endocochlear potential as a result of the different ion compositions of perilymph and endolymph is an important prerequisite for proper functioning of the hearing cascade. Thus, the buffer used to deliver vector preparations should be compatible with inner ear fluids and cell types. (3) Optimal delivery routes to administer viral vectors to the cochlea need to be investigated (Figure 2), and vector distribution and dissemination from the site of injection need to be characterized. (4) Pre-existing immunity to vector components, such as the capsid, or to transferred genes might limit gene transfer and/or expression efficiency, or cause local inflammation.

Currently, three main viral vector systems have emerged for inner ear gene therapy: (1) lentiviral (LV) vectors, (2) adenoviral vectors (AdV), and (3) adeno-associated viral (AAV) vectors. Each of these were tested in in vitro transduction experiments using cell lines, dissociated primary tissue and cochlear explants and were also characterized in vivo in rodent models. All three systems competently enter post-mitotic cells, and thus are suitable for inner ear cell transduction. Due to space limitations, we will primarily focus on LV and AAV vectors.

In contrast to AdV and AAV vector platforms, LV vectors stably anchor their genomic information into the host cell’s genome. While this feature is of great advantage when targeting dividing cells – guaranteeing stable, long-term gene addition and transmission to daughter cells – non-integrating vectors have a superior safety profile. Many of the specialized and treatment relevant otic cell types, such as hair cells (HC) and spiral ganglion neurons (SGN), are post-mitotic and thus compatible with non-integrating vector systems. Nevertheless, although naturally integration-competent, LV vectors can be rendered integration-deficient, e. g. upon catalytic inactivation of the viral integrase enzyme, creating so-called non-integrating LV (NILV) vectors. Although so far only the integrating LV vectors have been tested in the context of otic gene therapy settings, NILV vectors might emerge as attractive alternatives with improved safety profiles in the future.

A Speech and language therapist (SLT) is considered an expert in the treatment and management of communication and swallowing concerns across the lifespan. An SLT should have a comprehensive understanding of hearing and the auditory mechanism in order to identify individuals who may have impaired hearing, resulting in communication challenges. This report examines the different categories of hearing loss and the challenges and consequences that may arise for clients in this area.

A mild hearing loss is evident in air conduction thresholds within the 26dB HL to 40dB HL range. A mild hearing loss can result in inaccurate speech production and decreased participation amongst peers, (Stelmachowicz, Pittman, Hoover, Lewis & Moeller, 2004). This type of hearing loss can equate to an individual missing as much as 50% of a spoken conversation, resulting in difficulty developing appropriate language, social-emotional and academic skills, (Yoshinaga-Itano, Johnson, Carpenter & Brown, 2008). Consequences of a mild hearing loss are varying and impact individuals to different extents, however, it is important to note that the term ‘mild’ does not equate to insignificant or small challenges, (Welling & Ukstins, 2017).

A moderate hearing loss can be observed in an individual whose air conduction thresholds fall within 41dB to 55dB HL. This category of hearing loss can account for individuals missing as much as 80% of speech signals when verbally communicating, (Welling & Ukstins, 2017). It is suggested that full auditory access is integral for the development of appropriate speech and language in children and that this category of hearing loss is likely to result in delayed or incorrect syntax, a smaller vocabulary repertoire, inaccurate speech, and a flat voice, (Anderson & Matkin, 2007). Consequences for an adult with a moderate hearing loss are more concentrated on social effects, as adults are more likely to navigate their auditory challenges by using inference and life experience to fill gaps they encounter. Adults may decide they no longer enjoy participating in activities they once loved, such as going to the cinema, eating out at restaurants and being in settings that are loud and busy, (Dalton, et al, 2003).

A hearing loss evident in the range 71dB HL to 90dB HL is considered to be severe. For children who fall into this categorisation, it is imperative that early intervention takes place in order to improve the likelihood of speech and language acquisition within a relatively appropriate rate, (Tharpe, 2008). Individuals with a severe hearing loss may be unable to access any verbal conversation without supplements, (Welling & Ukstins, 2017). Educational impacts are evident in children with severe hearing loss, as individuals can become withdrawn due to being unable to access learning in the traditional format. Thus, these children don’t make the typical gains seen in their normal-hearing peers and can be much slower to reach educational milestones, (Marschark, Shaver, Nagle, & Newman, 2015). Adults can display a rapid decline of participation and are often seen to self-isolate due to feelings of disconnect and insecurity, (Blazer, 2018).

A conductive hearing loss (CHL) is diagnosed when an air-bone gap is evident. This occurs when an individual’s bone conduction thresholds are within normal limits, yet their air conduction thresholds show impairment, (Hsieh, Lin, Ho & Liu, 2009). A conductive hearing loss can result from damage to the outer and middle ear or may be due to abnormality or obstruction in this area. Typically, a conductive hearing loss is characterised by a reduction in sensitivity, rather than a loss of clarity, (Welling & Ukstins, 2017).

If an individual is observed to have air and bone conduction thresholds that are equally abnormal, they are considered to have a sensorineural hearing loss, (SHL). This occurs as a result of damage to the inner ear and auditory nerve and is considered to be permanent. Often a person with SHL can hear low frequency sounds better than sounds in the higher frequencies, (Khan et al, 2019).

An individual with SHL is likely to be more impaired than someone with CHL. This is in part due to the fact that SHL includes a loss of sensitivity similar to CHL but is often times more significant and far-reaching. This loss of sensitivity is in addition to an impaired ability to understand auditory information which is evident even with amplification. Furthermore, individuals with SHL are likely to experience symptoms such as vertigo, tinnitus and an abnormal rising loudness upon the identification of a sound, (Wroblewska-Seniuk, et al. 2018).

An SLT is likely to have an individual with a conductive hearing loss on their caseload at any given time. In this population, an SLT may require collaboration with an audiologist in order to provide the best evidence-based practice. An SLT may provide counselling in the form of emotional support to clients with a conductive hearing loss and their families. This would include addressing hearing loss concerns and the social and emotional consequences of hearing impairment. An SLT’s role also encompasses prevention and wellness by observing the quality of life and general wellbeing of clients in this population. Furthermore, advocation and education around hearing loss are paramount. It is the role of an SLT to identify individuals who may be displaying difficulties hearing, yet it is not within their scope of practice to evaluate or diagnose a hearing impairment. Additionally, it is the role of an SLT to maintain audiology instrumentation used for conductive hearing loss. Finally, it is the role of an SLT to ensure clients and their families receive the most beneficial service, therapy, and support in alignment with a client centred practice, (Welling & Ukstins, 2017).

In consideration with the above, it is important for an SLT to consider the implications of a hearing loss on all aspects of a client’s life. By doing so an SLT is employing the use of client-centered practice and ensuring a holistic view is being maintained in the management of each client. The following themes are important considerations for this population of clients and should be closely monitored to ensure social-emotional wellbeing.

Social isolation

People with hearing impairment can become withdrawn and avoid instances where they will be required to communicate. Thus, there appears to be a strong relationship between hearing loss and social isolation, (Mick, Kawachi & Lin, 2014). Furthermore, it has been reported that children with hearing loss have greater difficulty forming positive relationships with their typically hearing peers, (Martin, Bat-Chava, Lalwani & Waltzman, 2010). It is often reported that people with hearing loss will exclude themselves from family gatherings to avoid demonstrating difficulty in front of loved ones, (Welling & Ukstins, 2017).

Depression

It has been concluded that individuals with hearing loss are at significant risk for psychiatric symptoms such as anxiety and depression, (Blazer, 2018). The inability to access information in traditional ways can cause feelings of worthlessness and low self-esteem, which result in lowered mental health status, (Weinstein, & Crofts, 2018). Research indicates that hearing loss can double the likelihood of developing depression and anxiety across the lifespan when compared to typically hearing individuals, (Kvam, Loeb, & Tambs, 2007).

Educational achievement

Research by Most (2004) suggested that children with mild hearing loss demonstrate lower performance in the classroom than children identified as having a more severe hearing loss, this is likely a consequence of accessibility to supports being lower for less significant hearing loss. Dalton, (2013) suggested that students presenting a mild hearing loss are likely to exert greater energy expenditure than their peers, impacting their ability to process the information around them. Alternately, children with moderate hearing loss were observed to make adequate academic progress when compared to their peers with typical hearing, (Antia, Jones, Reed & Kreimeyer, 2009). This could be because of the additional supports put in place for these children. Children with severe hearing loss often cannot access any verbal information or instruction within the classroom without additional support. They are often unable to participate and show significantly lowered educational attainment when compared to their typically hearing peers, (Marschark, Shaver, Nagle, & Newman, 2015).

The following reflection is based on my own experience using earplugs to simulate having a moderate hearing loss. I found this experience incredibly challenging. Not only was it difficult to have an impairment of hearing, but I felt I was inconveniencing others. I found it difficult to ask for help and found that the environment played a huge role in my level of understanding. For example, within my own home, I felt I was better able to adjust external influences, i.e., I could turn off the extractor fan and turn up the tv to better my chances of hearing what was being said. Thus, the task where I watched television was the easiest.

When using earplugs to watch television, I had to ask my friends to constantly adjust the volume. My friends also complained that once I found a comfortable volume for myself, it was too loud for them to enjoy the program we were viewing together. The volume was significantly higher than I am used to, with usual ranges being 15-20 and adjusted to approximately 40 during this experiment. The premise of the show we were watching made this task difficult as well due to the fantasy theme that was evident, meaning I could not always infer what was happening or what would come next. Once I took the earplugs out, I had to go back to the beginning as I had not taken in a lot of information.

Following this, we watched a segment of the news. This was much easier to follow, perhaps because I could use my inferencing skills to fill in details that were not heard. The absence of background sound made this part of the task much easier and the ability to see the speakers face allowed me to lip-read to some extent.

In the café setting, I could not control the level of noise happening around me, which made following the conversation challenging. I found that I was constantly asking for clarification on what was being said and asking friends to repeat themselves a number of times. The noise and environment made conversing really difficult and I felt very aware that my own voice was raised more so than others. When ordering my drink, I did not anticipate that the waitress would ask me follow up questions and was unprepared for having to navigate conversing with her. I felt uncomfortable and after explaining to her that I was completing an assignment I took out the earplugs and gave up.

I found the café scenario particularly unpleasant and the most difficult, due to the added component of unfamiliar people. When in the café I felt that I had to advocate for myself so much more, asking the waitress to repeat herself and attempting to clarify what she was saying. This was the most difficult part of the experiment in my opinion.

While wearing earplugs to my paediatric dysphagia lecture on a Monday morning, I found myself losing motivation incredibly quickly. I could not keep up with what the lecturer was saying and found myself reading off of the slides rather than following her verbal language. I found that I was exerting so much effort for minimal return. I tried to rely on my hearing but found that the more I focussed on listening the more irritated I became.

The thing that surprised me most about this experiment was the way in which my hearing impairment impacted other people. I found that in order to accommodate for my disability other people were having to adjust their own way of living. For example, turning up the tv supported my ability to hear but was actually too loud for my friends. Furthermore, when I couldn’t understand what was being said they had to slow down their speech, often times choosing keywords and over articulating to further support my receptive input.

With earplugs in I experienced a hearing loss that ranged from mild to moderately severe. Upon consideration of the mean results of my audiogram I mostly experienced a moderate hearing loss. I believe that this reflected the difficulties that I encountered relatively well, however; I do believe I was unprepared for how challenging I would find this experiment. Over the course of the different tasks, I learnt how frustrating and time consuming every-day activities can be for a person with hearing loss.

Hearing loss is when your ability to hear is reduced. Hearing loss can develop by two main factors, exposure to loud noise for an extended amount of time and/or ageing. Noise induced hearing loss is often sensorineural, this is where the problem lies between the inner ear and the brain. The world is a loud environment, in the average everyday life the ear is exposed to a wide range of harming decibels. In this essay on hearing loss the focus will be on noise-induced hearing loss with the following being considered; how we perceive loudness including the structure of the ear and how it can become damaged, places, devices and levels and how these can become factors into hearing loss, the last subject will be the law and how requirements in the workplace and in live music events can help with the effect of hearing loss.

The ear is split into three main sections, the outer ear, middle ear and inner ear. The outer ear consists of the pinna, which acts as a funnel to direct the sound further into the ear, and the auditory canal (also known as the ear canal) this sends the sound from the pinna to the eardrum. The final part of the outer ear is the tympanic membrane, more commonly known as the ear drum, this sends the sound vibrations into the inner ear. The middle ear includes three small bones, the malleus, incus, and stapes, that join up to be the ossicles. The malleus joins to the eardrum, which then goes along to the stapes which is connected to the inner ear. The inner ear connects to the middle ear via an oval window, this then connects to the cochlea. The cochlea is fluid filled and contains many hair cells which are vital to hear. When a sound is made the vibrations travel down the pinna, to the eardrum which vibrates, these vibrations are then transferred to the inner ear via the bones in the middle ear, from there the vibrations are sent into the fluid in the cochlea which is where the pressure waves are created, a pressure difference is created across the membrane.

The National Centre for Environmental Health (2018) state that “The average person is born with 16,000 hair cells in the cochlea” Loud noises can cause the hair cells to bend over causing temporary hearing loss, however, if there is repeated exposure to loud noises then these hair cells may be destroyed, once destroyed they are not repairable. Noise not only damages the hair cells but also can damage the auditory nerve that carries information to the brain.

“Loudness is commonly confused with volume. The two terms, however, are entirely different concepts’, – award winning audio engineer Brad Pack (2019) says. “Volume is a scientific measurement of the quantity or power of a sound. Loudness, on the other hand, is much more difficult to quantify as it is completely subjective and based entirely on your personal perception of sound. The frequency content, duration, and volume of a sound are all factors in how we perceive its loudness”, – he continues. Points from this is that loudness is a subjective opinion based off of personal experience, and what we actually perceive loudness is a group of factors together.

Hearing protection is important from a young age, if a child is exposed to loud noises, they are susceptible to acoustic trauma, which is an injury to the inner ear. Hearing protection devices can be used to help reduce the noise that is transmitted to the eardrum. (Doswell Royster, 2017, 113-117). By using hearing protection, the impact on the inner ear will be lessened therefore protecting the cochlea and reducing the risk of hearing loss. Devices such as earplugs, noise cancelling headphones and noise isolating headphones can all help protect against the excess sound pressures.

The architecture and what sort of building can affect how noise travels and is being transmitted. For example, a study by Walsh et al. (2000) done in San Francisco found that when measuring the decibels of most popular clubs, the loudest was 105 decibels, and the quietest was 94 decibels. The human ear is at risk of damage past 85 decibels. The National Institute for occupational safety and health say that in the quietest club, it would only take up to an hour before people are at risk of hearing damage, at the loudest it would only take 4 minutes.

The study by Walsh et al. (2000) is a look into a club scenario, industrial workplaces are also a common place that comes up when discussing noise induced hearing loss, there was an estimated 21,000 numbers with work related hearing loss from 2017 – 2018 (HSE, 2019).

Victory (2019) discusses the impacts that earphones and headphones can have on a listener. “Most earbuds are low quality, incapable of blocking out ambient noise. They tend to transmit bass poorly. Both of these factors lead listeners to turn up the volume even more”. Victory then goes on to talk about safer alternatives to headphones which include noise cancelling headphones, which use inverse waves to cancel out any other sounds, and noise isolating headphones, which create a seal around the ear to isolate the sound, blocking out any unwanted noise. Headphones and earphones that cause listeners to turn up the volume can damage the listeners ears as when the volume is turned up, the decibel increases but also that listener then becomes accustomed to that volume.

“Level is a term with precise meaning. For a real sound travelling in air (or any other medium), its level is measure in terms of sound pressure. Sound pressure is the difference from normal air pressure caused by the sound”, – David Mellor (2006) explains. The higher the sound level, the more likely the noise could damage the inner ear.

In 2006 a noise regulation was put in place to help workers protect their ears from excessive noises at the workplace. The regulation states that any worker exposed to noise of 80-87dB must be provided with a form of ear protection (The control of noise at work regulations (2005)). This did not apply to entertainment or music workplaces as that didn’t join the regulation until 2008, as it was considered that the music industry, noise is purposefully created for enjoyment, whereas in other workplaces, such as a factory, the noise is an excess from the machines. However, it was agreed that it was necessary for the entertainment sector to protect the employees from any damage.

According to the Health a Safety executive (2019) there is no specific legislation setting noise limits for events. However, it also states that no audience areas can be exposed to more than 140dBs, as well as no audience members are allowed within 3 metres of a loudspeaker. And finally, if the event is likely to exceed 96dBs, then the audience must be told of the risk before the event. If an event has pyrotechnics, the same applies that it cannot exceed 140dBs, and the audience must be aware.

Some reports mention excessive noise levels in the case of a cinema, when tested by Ferguson et al. (2000), all films were below 80dB, however, they did exceed 90dB but it was only for a few seconds. They found that there was no evidence that cinemas could cause hearing loss.

The report was to explore into hearing loss and how damage to the ear can be prevented. Damage done to the inner ear is usually irreversible, however, if following the correct regulations risk of damage can be reduced. When put into real life circumstances, in my personal experience, hearing loss can be difficult to deal with. A companion of mine did not use hearing protection, through the beginning of his music career, where he was in a wedding band, whilst at the same time producing his own music. His ears soon developed permanent tinnitus, causing him to hear a constant ring. Damage to ears can happen to everyone, and it is important to protect them especially in younger children. As he was in a band he had frequent exposure to loud sound which, without protection, after a while causes pressure on the inner ear, which is what happened causing tinnitus. In the future to protect my ears from any damage I will use earplugs when I know I’m going to be exposed to loud noises and as Victory (2019) mentioned that most earphones have factors that cause listeners to turn up their music, therefore I will use suitable headphones when listening to music.

What is hearing loss? One of the less frequently asked questions, for obvious reasons which is it is something seem to be not so vital. Until it happens to you which will be too late. I can confidently say I am very fortunate to be part of the masses that were taught and enlightened about hearing loss at a young age, of which I still wish I knew about it way earlier. As an aspiring sound engineer studying at an Academy of Sound Engineering, in one of first year industry lectures we were visited by a qualified Audiologist. An Audiologist is a licensed healthcare professional who specializes in diagnosing and treating hearing, balance and tinnitus disorders. We shall discuss further about the disorders as we go along with the content. The experience was very enlightening and the information presented to us was very helpful. Since the day I was enlightened about hearing loss I became more cautious about my hearing especially in a music environment. Hellen Keller once said “Blindness separates us from things but deafness separates us from people”. Hearing loss is when your ability to hear is reduced. A hearing loss makes it more difficult for you to hear speech and other sounds. Like any other diseases hearing loss is very dangerous.

Experiencing hearing loss feels like the world is fading away but it is actually getting louder day by day. Think about couple of centuries back when people could hear themselves think wherever they are compared to now whereby you have to spend a fortune to find a quiet, peaceful place to hear yourself think. What I am trying to prove is the fact that the land is filled with distractive noise pollution. Noise pollution that does not only affect humans but all living species.

Hearing loss have a lot of various causes. Noise is a common cause, depending on the filled you are most exposed to. You can be more exposed to live music environment like outdoor or indoor music festivals, Mining and factory industry, where you find big machines being operated. International airports, where enormous aeroplanes are based; being in the city more frequent. Age is considered as a natural cause of hearing loss of which is beyond our control. As we grow our hearing ability worsens in our 40s and onwards and when we reach our 80s, more than half of us suffer from significant hearing loss. Age-related hearing loss is also called as Presbycusis.

As an aspiring sound engineer and musician I believe that my hearing is my highly valuable asset, without my hearing there is no future in these industry, yes it is arguable, I believe a thesis can becompiled on making music with hearing loss. In audio industry 99 percent of the work is based on hearing hence the word “audio” suggests. You find live sound engineering where a sound engineering operates the sound from front of sound and they compelled to be active at all times, therefore they are exposed to high amount sound for consecutive house of the show. It runs down to being in a studio as a producer, broadcaster or post production where there is not much of noise compared to live sound environment, but you get to be exposed to the same sounds constantly for the time you are active on a project. Tinnitus are one of the symptoms audio technicians, musicians and audience experience after being in loud music environment. Tinnitus is the constant hearing of a sound when there is no sound present. Some describes it as a ringing sound, a hiss, or a high pitch tone. Tinnitus is caused by either a single extremely loud sound or by loud sounds over a period of time. You can imagine how sound engineers stand a chance to be attacked by tinnitus multiple times. Using earplugs is the best solution to this adverse situation.

“Noise induced hearing loss”, according to my point this is one of the statements taken for granted till you notice the following symptoms of hearing loss: missing words, TV or radio volume louder than usual, blocked feeling in ears, struggling to hear in noisy environment, tinnitus.

There are different types of hearing loss. A hearing loss can be sensorineural which results from damage to the tiny hair cells in the inner ear. Presbycusis is a type sensorineural hearing loss. A conductive hearing loss is where the ears’ ability to conduct sound from the outer ear through the middle ear into the inner ear is blocked or reduced. Mixed hearing loss is a combination of a conductive hearing loss and a sensorineural hearing loss which results to having a difficulty to conducting sound to the inner ear, and the hair cells in the inner ear are damaged at the same time, of which in my point and experience it happens rarely. A hearing loss can also be a bilateral hearing loss or a single-sided hearing loss. As the word bilateral suggests it simply means you can experience hearing loss in both ears and single-sided hearing is experiencing hearing loss in one ear also know as unilateral hearing loss.

Hearing loss impacts our emotional well-being. I mean you can imagine when we hear our best, there is nothing stopping us from enjoying the sounds of laughter, music, nature or conversation with family and friends. These sounds help us, and undeniably make moments more memorable and life more enjoyable.

Can hearing loss be prevented? We live in a society which noice is a natural part of everyday life, irregardless whether bad or good, and with our ears being such delicate organs, we must take of them. Yes, hearing loss can be prevented. Using earplugs as mentioned earlier on is one of the most effective prevention reason being it reduce noice by 20 to 30 dB. Bare in mind the threshold of human hearing is 0 dB up to 130 dB. We are even exposed to noise in our home, but a few precautions and changes can make all the difference, for example installing carpets, upholstered, furniture, curtains and other soft materials can absorb the worst of the noise.

The challenge hearing loss presents to someone who pursuing a career in sound engineering is the fact that they will loose almost every detail of the event. All the way from communicating with the team, to operating the sound, for example in a live music environment, it will be hard to hear from the front of house which will result to increasing audio level above the required maximum level of which might sabotage the whole event.

Robert Frost once said “The ear is the only true writer and only true reader”. It will smart of us to take good care of our hearing to be able to hear the first words of our grandchildren. It will be smart of us to work on reducing noise for the sake of noise pollution and all the living species in our planet. Let us consult with our nearest audiologist to find out about our hearing status.

Based on a research, it has been estimated that Unilateral Hearing Loss (UHL) are more likely to occur in 0.83/1,000 newborn children (Prieve& Stevens, 2000). Children with UHL face a unique set of challenges as they grow older (Bess & Tharpe, 1984; Culbertson & Gilbert, 1986; Giolas & Wark, 2014). According to American Speech-Language-Hearing Association, UHL defines as having normal hearing in one ear but there is hearing loss in the other ear where it may be a range from mild to moderate and it may affect both children and adults. In most cases, the effect of UHL has not been studied deeply. Thus, in this essay we will talk more in detail about the adverse repercussions of UHL in children.

Firstly, children with UHL experience difficulties in sound localization, as they do not have binaural hearing ability. Binaural hearing ability is required for development of auditory processing and perception (Rohlfs et al., 2017). Localization of sound source in space is harder without binaural hearing (Lieu, 2004). The lack of head shadow effect in children with UHL results in poor directional hearing. This is due to the lack of inter-aural level difference (ILD) which is the head and pinna attenuates sound at far ear while boosts sound at near ear. In this case, the lack of ILD affects the head shadow and cocktail party effects to come into play to allow sound localization and spatial hearing. UHL leads to sound localizing error according to the severity of UHL in children. Thus, UHL affects the ability to localize the sound in children with UHL.

Ordinarily, there are high possibilities for a child that passed newborn hearing screening to have late-onset UHL undetected over the years. This may affect the development of language and speech of the child as they grow. Children with UHL are proven to have speech and language delay, where they demonstrated poor cognitive and oral language scores, especially among children with severe to profound sensorineural hearing loss, when compared to normal hearing children (Anne, Lieu, & Cohen, 2017). UHL is also closely associated with significant negative scores on standardized speech language test (Lieu, Tye-Murray, Karzon, & Piccirillo, 2010). This could be due to children with UHL activate attention networks less strongly compared to normal hearing children, thus causing memory, learning and attention deficits (Vila & Lieu, 2015). They may also face problems in sound localization and speech discrimination in noise, which is the utmost importance of binaural hearing (Yoshinaga-Itano, Johnson, Carpenter, & Brown, 2008). Children with UHL may have difficulties in allocating and focusing on the teacher’s voice, and it is hard for them to discriminate between phonemes thus it is onerous for them to acquire speech correctly. Speech and language delay will also lead to academic failures.

UHL in school-age children mayaffect their academic performances in school. Many studies have reported on school-age children with UHL seem to have increased rates of grade failures, need for additional educational assistance, and perceived behavioural issues in the classroom (Kuppler, Lewis, & Evans, 2013; Lieu, 2013). Their parents also noticed some difficulties in their children when learning at school, especially when the class is very noisy (Lieu, 2004). This is because the noise will mask the teacher’s voice and this may lead to difficulty in speech discrimination, thus they may be unable to obtain all the information given by the teacher. Hence, this will affect their understanding in class. Besides, children with severe UHL (60 dB HL) had a significantly lower IQ score (Kuppler et al., 2013). They may not be able to perform well in academic learning. To cut short, children with UHL have poorer academic performances compared to normal hearing students.

In addition, UHL does not only affect the children’s academic performances, it also increases the risk of developing social skills difficulties. Children with unilateral mild hearing loss (UMHL) had lower social skills than the typical hearing (TH) children (Laugen, Jacobsen, Rieffe, & Wichstrom, 2017). This is because during a conversation they might not be able to hear clearly if others speak softly. Things will be even worse when they have a noisy background. The results suggest that despite a limited effect on vocabulary development, early intervention is likely to promote social skills development in children with UMHL (Laugen et al., 2017).

In conclusion, UHL has affected the quality of the children’s life in the aspects of sound localization, speech and language delay, academic performances and social skills.Therefore, with some early interventions and many efforts from parents and teachers, the quality of life can be improved. It is also an important step to ensure that hearing screening is being done throughout childhood, especially on children with high-risk factors.

Bibliography

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2. Kuppler, K., Lewis, M., & Evans, A. K. (2013). A review of unilateral hearing loss and academic performance: Is it time to reassess traditional dogmata? International Journal of Pediatric Otorhinolaryngology. https://doi.org/10.1016/j.ijporl.2013.01.014
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