SAFETY SATURDAY: NOISE

…Which meets all motion and becomes its soul,

A light in sound, a sound-like power in light,

Rhythm in all thought, and joyance everywhere—

Methinks, it should have been impossible

Not to love all things in a world so filled;

Where the breeze warbles, and the mute still air

Is Music slumbering on her instrument.

- The Eolian Harp - Samuel Taylor Coleridge

Sound energy is mechanical energy produced by the displacement of a conducting substance (Pain, 2005). Most commonly, sound energy is transmitted as vibration through the air from a source to a receiver - the simple example is of one person speaking to another, where the sound energy produced by the speaker is perceived by the listener. Sound energy is a mechanical vibration, and so can be considered within the context of vibration energy as a whole, but considering safety with respect to sound energy also necessitates consideration of human hearing and audiological health. All mechanical energy that reaches the ears can affect hearing, whether that energy is transmitted through the air, through the body, or directly through the bones of the skull. Sound energy can be generated from physical processes like tool use, material contact, and something as simple as the action of a keyboard (Suter, 2002). Sound can be used in speech and alarms to convey information, to indicate machine operation, or as part of signalling. Sound is comprehensible when that sound conveys information - again speech is an example of this, as are alarms, audio tones, and audio signals (Kanulainen et. al., 2009). Sound is distinct from noise - noise is unwanted, unwelcome, or unpleasant sound (Bijsterveld, 2008). Noise therefore may be any sound that introduces interruption, distraction, or causes distress without causing pain. Noise has two components: the frequency of the noise measured in Hertz (Hz) referring to how high or low the note of the noise may sound, and the sound intensity measured in Decibels (Db) which is a measure of the sound energy. This discussion will focus on noise resulting from sound energy that is applied in harmful doses to the ears of a worker, and will not consider the cognitive, attentional, or specific performance effects of excess noise. 

Human hearing is the physiological process through which sound energy in the environment is transduced from mechanical vibration of the air into comprehensible information by the mechanical apparatus of the outer and inner ear, the auditory cortex, and the brain more generally (Gefland, 2017). Mechanical agitations in the air stimulate the membranes of the ear, which transmit these vibrations into the bones of the ear, which in turn beat against the inner ear. The action of the bones against the inner ear creates movement within the fluid of the inner ear, which transmit the mechanical agitation of outside vibrating air into fluid vibrations in the inner ear, specifically in the cochlea. To this point, hearing is only a matter of physical forces, but the vibration of the fluid of the inner ear stimulates cells within the cochlear spiral which are affected by and so transduce physical stimulation into neural signals. These nerve signals are then transmitted to the auditory cortex through the auditory nerve (Webster & Fay, 2013), where those signals are integrated by the brain more generally and processed into comprehensible information. Hearing is the process through which the movement of mechanically agitated air is transduced into recognisable sounds like speech, music, instruction, warning, and direction. It is a physical, physiological, and neurological phenomenon that requires attention, consideration, action, and discretion. The challenge is that the ears do not discriminate in terms of the physical energy that reaches them - sound energy of all loudnesses, frequencies, and natures reaches the ear, and it is the brain’s job to sort them out. Hearing loss can occur in two broad categories - conductive hearing loss, and sensorineural hearing loss (Lee & Bance, 2019). Conductive hearing loss is a disruption in the effectiveness of ear structures in translating sound energy from the environment to the inner ear, due to age, fluid in the inner ear, trauma, or infection (Zahnert, 2011). Sensorineural hearing loss is the consequence of damage to the cells of the inner ear, the auditory nerve, and / or the auditory cortex (Tanna et. al., 2020). Hearing loss often occurs naturally as a consequence of ageing (Suzuki et. al., 2012). In spite of this, the profoundness of hearing loss as well as the range of hearing that is lost may be affected by occupational factors. Because of this, it is important to consider protection of human hearing from both physical and neurological approaches.

Before considering noise hearing loss itself, other impacts of sound energy may be discussed. Noise is unwanted sound that is within the range of human hearing and perception, however sound energy may be applied to the human body at frequencies and intensities that cannot be perceived but which may still cause health effects. Infrasound is sound energy that is applied at less than 20 Hz frequency. Infrasonic sound arises from unbalanced, low-tempo fans, from traffic, from turbines, from railway ballast, and from other everyday sources (Baliatsas et. al., 2016). Sustained exposure to low-frequency and infrasonic noise can cause nausea, headaches, fatigue, and changes in sleep quality (Bolin et. al., 2011; Persinger, 2014). Where humans are exposed to sound frequencies above 20,000 Hertz, or 20 Kilohertz, this sound is described as ultrasound. Common sources of sound above 20,000 Hz include ultrasonic welding machines, silencers, and steam valves. Ultrasonic exposure may result in headaches, or adverse impacts on the nervous system, though research is still being conducted in this respect. 

The most common examples of potential sources of occupational noise exposure within the normal range of human hearing, being 20 Hertz to 20 Kilohertz are industrial, construction, extraction, transportation, and agricultural industries generally (Liebenberg, 2023). Hazardous Noise is sound energy whose dose over a sufficient amount of time is likely to cause injury to the inner ear. A sufficiently large dose of noise over time may cause temporary deafness, which is referred to as temporary threshold shift (Melnick, 1991). This temporary deafness is the result of an overexposure to unattenuated sound energy, such as might be experienced when attending a band show without hearing protection. The overstimulation of the transducing cells in the inner ears results in cellular changes which are different to those that occur when the ears are permanently damaged (Mills et. al., 1979; Nordmann et. al., 2000). It is reversible because the cells can recover, but this capacity diminishes with age. In cases of sustained exposure to sound energy that exceeds the ear cells’ capacity to recover, or in cases where the sound energy to which the ear cells are exposed is excessive to a dangerous degree, permanent hearing loss may occur, referred to as permanent threshold shift (Quaranta et. al., 1998). Permanent sensorineural hearing loss is typically irreversible, and persists following a period in which a temporary threshold shift might otherwise have resolved (Ryan et. al., 2016). This is referred to as noise-induced hearing loss. Most incidences of noise-induced hearing loss arise from slow progressive degeneration of the cells in the inner ear through exposure to prolonged, excessive noise. 

In Australia, the Model Work Health and Safety Regulations (Safe Work Australia, 2023a) state that the exposure standard for noise is an LAeq,8h of 85 dB(A) or an Lcpeak of 140 dB(C), in line with AS/NZS 1269.1:2005. This means that a person working on a shift is exposed to hazardous noise where that noise exceeds 140 dB(C) in a single instance, or where the cumulative dose exceeds 85 dB(A) over an eight hour equivalent. An eight-hour equivalent is the normalised time of exposure, which is important where workers are working for longer than eight hours, as their noise dose may be larger as a consequence of their extended shifts even if the noise to which they are exposed is less than 85 dB(A). This is notable as workers in high-likelihood exposure industries like construction may work shifts longer than 8 hours (Lewkowski et. al., 2018), and 32% of Australian workers reported usually working extra hours or overtime when assessed in August 2024  (Australian Bureau of Statistics, 2024). Hand-arm vibration and whole-body vibration may also increase the risk of hearing loss in the workplace, as well as a worker’s exposure to substances and chemicals that can affect the health of the cells of the inner ear (SWA, 2018). Safe Work Australia’s Beta Occupational Hazards Dataset reported that 2.73 million people were exposed at least once a week to distracting or uncomfortable sounds and noise levels (SWA, 2023b). The most likely occupations were process workers, operators, drovers, and construction workers, as shown below in Figure 1.

Figure 1

Top 10 Occupations by Exposure Score to Sounds and Noise Levels that are Distracting or Uncomfortable

Note. Adapted from Safe Work Australia. (2023). Insights from the Beta Occupational Hazards 

Dataset.

The same dataset shows that a very small rate of claims are caused by sound and pressure, yet the Exposure to Noise and Ototoxic Chemicals in the Australian Workforce Study undertaken by Lewkowsi et. al. (2019) reported that in Australian workforce, 19.5% of men and 2.8% of women exceeded the recommended full shift noise limit of 85 dBA during their last working day, and men were more likely to be exposed to noise if they were younger, had trade qualifications and did not live in a major city, as well as being more likely to be exposed to workplace ototoxic chemicals, and one-in-twenty appeared to be exposed to vibration that exceeded safe thresholds (Lewkowski et. al., 2021).

In 2006, compensation claims made due to deafness represented 19% of all disease-related claims made, and while this number is lower due to changes made in manufacturing, the main cause remained prolonged exposure to noise (Safe Work Australia, 2006) where the implication is that the number of workers exposed to hazardous noise may be reasonably inferred to be higher than the number who make claims for compensation. Safe Work Australia also notes in their Occupational Noise-Induced Hearing Loss in Australia report (2010) that noise mitigation progress in small business, where knowledge is insufficient and there are mistaken beliefs about the time-course and effect of hearing loss, the effectiveness of controls is diminished (SWA, 2010). The impact of this is that risk is concentrated within those professions which produce hazardous noise as a consequence of normal work, but again amplified by business and worksite factors that may predispose workers to increased risk. Machinery operators, tradesworkers and labourers work with tools, for extended shifts, and in nonstandardisable conditions, resulting in increased exposure to hazardous, distracting, or otherwise uncomfortable noise, as shown below in Figure 2.

Figure 2

Median Exposure scores for selected job hazards and environmental conditions, by occupation group

Note.  Adapted from Safe Work Australia. (2023). Insights from the Beta Occupational Hazards Dataset.

Managing the risk of hazardous sound energy is a matter of managing the generation, path, and reception of that energy from its source to its receiver. Personal hearing protection may be effective in mitigating exposure to excess noise (Daniel, 2007), but this minimises the reception of noise energy at the point of the worker as an individual and does not minimise the noise generated. Additionally, adherence to personalised noise protection is typically poor (Couth et. al., 2022) and so relying on an individual worker to mitigate their risk is generally a last-resort. Where possible, reducing shift times to bring worker exposure in line with standard and minimise excessive sound energy dose is effective in minimising the effect of hazardous noise (Rerkjirattikal & Olapiriyakul, 2021). However, this too relies on administrative controls undertaken at the worker level, and so may not be generalisable or reliable. Controlling the transmission of noise through space can be done by using interferential air or barriers where the source of noise is static powered plant such as a generator (Laxmi, 2024). Where the noise is the result of a portable powered plant, such as an impact wrench, saw, cutting blade or other powered implement, the source of the noise is necessarily close to the worker. In this case, control of hazardous noise is assumed to be built into the design of the tool as a matter of practical engineering, but the fact remains that patterns of use, posture, and other uncontrolled factors can introduce risk from sources that may not have been accounted for in the engineering phase. A combination of noise-mitigating interventions undertaken within the workplace are most effective, as suggested in Figure 3.

Figure 3

Examples of noise control measures in an industrial building

Note. Adapted from Safe Work Australia. (2018). Code of Practice: Managing noise and preventing hearing loss at work

Noise control programs may be effective means of minimising exposure to hazardous noise (SWA, 2010) wherein the control of noise exposure is undertaken as a matter of business planning and space design so as to minimise its end impact in operations through working shifts. However, this requires consideration of building planning and may require resources beyond the practical access of small businesses, or even the practical implementation of a workforce where the work is dynamic. Materials choices in building design or even the post-completion use of acoustic foam may be practical in absorbing noise from sources and minimising its resonance and echo in enclosed spaces (Kishore et. al., 2021), but these are, again, after-the-fact consideration. The situation remains that noise is a ubiquitous output of mechanical activity and physical work (Fahy & Thompson, 2015) and so there will always be some exposure. Additionally, workers are exposed to noise from activities outside those they undertake in their occupations, such as music shows, singing, movie-watching, and sports with loud noises such as shooting, motor racing, or anything to do with tools and mechanics. To this end, noise protection programs in workplaces may be appropriate, where noise doses are regularly assessed and workers’ hearing is regularly checked to ensure that potential hearing loss is addressed speedily (Williams et. al., 2007).

People are exposed to sound energy from the moment they are born. Most humans are innately able to generate sound by virtue of their vocal cords, by interacting with their environment, and incidentally throughout the day. The world navigated by workers and humans is one in which technological progress has allowed mechanical, chemical, physical, and other forms of work to be assisted and eliminated by using machines and tools to do that work. In using tools and machines to do different forms of work, workers and humans expose themselves to forces incidentally, implicitly, and intimately throughout their day. It is vital to remember that work engages the same physical capacities with which people enjoy and enrich their own lives - conversation, speech, music, and art all rely on a human’s sense of hearing and audiological health. 

None of this information constitutes medical, legal, occupational health and safety, best guidance, standard, or other guidance, instruction, or prescription. 

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References

Australian Bureau of Statistics. (2024). Working Arrangements. Retrieved 1 March 2025 from https://www.abs.gov.au/statistics/labour/earnings-and-working-conditions/working-arrangements/latest-release

Baliatsas, C., van Kamp, I., van Poll, R., & Yzermans, J. (2016). Health effects from low-frequency noise and infrasound in the general population: Is it time to listen? A systematic review of observational studies. Science of the Total Environment, 557, 163-169.

Bijsterveld, K. (2008). Mechanical sound: Technology, culture, and public problems of noise in the twentieth century. MIT press.

Bolin, K., Bluhm, G., Eriksson, G., & Nilsson, M. E. (2011). Infrasound and low frequency noise from wind turbines: exposure and healtheffects. Environmental research letters, 6(3), 035103.

Couth, S., Loughran, M. T., Plack, C. J., Moore, D. R., Munro, K. J., Ginsborg, J., Dawes, P., & Armitage, C. J. (2022). Identifying barriers and facilitators of hearing protection use in early-career musicians: a basis for designing interventions to promote uptake and sustained use. International Journal of Audiology, 61(6), 463-472.

Daniel, E. (2007). Noise and hearing loss: a review. Journal of School Health, 77(5), 225-231.

Fahy, F., & Thompson, D. (Eds.). (2015). Fundamentals of sound and vibration. CRC press.

Gelfand, S. A. (2017). Hearing: An introduction to psychological and physiological acoustics. CRC Press.

Kainulainen, A., Turunen, M., & Hakulinen, J. (2009). Awareness information with speech and sound. In Awareness Systems: Advances in Theory, Methodology and Design (pp. 231-256). London: Springer London.

Kishore, S. E., Sujithra, R., & Dhatreyi, B. (2021). A review on latest acoustic noise mitigation materials. Materials Today: Proceedings, 47, 4700-4707.

Laxmi, V. (2024). Transmission Path Control of Noise Pollution. In Handbook of Vibroacoustics, Noise and Harshness (pp. 273-302). Singapore: Springer Nature Singapore.

Lee, J. W., & Bance, M. L. (2019). Hearing loss. Practical neurology, 19(1), 28-35.

Lewkowski, K., Li, I. W., Fritschi, L., Williams, W., & Heyworth, J. S. (2018). A systematic review of full-shift, noise exposure levels among construction workers: are we improving?. Annals of work exposures and health, 62(7), 771-782.

Lewkowski, K., Heyworth, J. S., Li, I. W., Williams, W., McCausland, K., Gray, C., Ytterstad, E., Glass, D.C., Fuente, A., Si, S. Florath, I., & Fritschi, L. (2019). Exposure to noise and ototoxic chemicals in the Australian workforce. Occupational and environmental medicine, 76(5), 341-348.

Lewkowski, K., Ytterstad, E., Pugliese, M. J., McCausland, K., Heyworth, J. S., Li, I. W., Pettersson, H., Williams, W., & Fritschi, L. (2021). Exposure to hand-arm vibration in the Australian Workforce. Annals of Work Exposures and Health, 65(6), 659-667.

Liebenberg, A. (2023). Occupational Hearing Loss in Australian Mining: Prevalence, Management, and Prevention. Doctoral Dissertation, Edith Cowan University.

Melnick, W. (1991). Human temporary threshold shift (TTS) and damage risk. The Journal of the Acoustical Society of America, 90(1), 147-154.

Mills, J. H., Gilbert, R. M., & Adkins, W. Y. (1979). Temporary threshold shifts in humans exposed to octave bands of noise for 16 to 24 hours. The Journal of the Acoustical Society of America, 65(5), 1238-1248.

Nordmann, A. S., Bohne, B. A., & Harding, G. W. (2000). Histopathological differences between temporary and permanent threshold shift. Hearing research, 139(1-2), 13-30.

Pain, H. J. (2005). The physics of vibrations and waves. Sixth Edition. John Wiley & Sons, USA

Persinger, M. A. (2014). Infrasound, human health, and adaptation: an integrative overview of recondite hazards in a complex environment. Natural Hazards, 70(1), 501-525.

Quaranta, A., Portalatini, P., & Henderson, D. (1998). Temporary and permanent threshold shift: an overview. Scandinavian audiology. Supplementum, 48, 75-86.

Rerkjirattikal, P., & Olapiriyakul, S. (2021). Noise-safe job rotation in multi-workday scheduling considering skill and demand requirements. Journal of Industrial and Production Engineering, 38(8), 618-627.

Ryan, A. F., Kujawa, S. G., Hammill, T., Le Prell, C., & Kil, J. (2016). Temporary and permanent noise-induced threshold shifts: a review of basic and clinical observations. Otology & Neurotology, 37(8), e271-e275.

Safe Work Australia. (2006). Work Related Noise Induced Hearing Loss in Australia. Retrieved 1 March 2025 from https://www.safeworkaustralia.gov.au/system/files/documents/1702/workrelated_noise_induced_hearing.pdf

Safe Work Australia. (2010). Occupational Noise-Induced Hearing Loss in Australia. Retrieved 1 March 2025 from https://www.safeworkaustralia.gov.au/system/files/documents/1702/occupational_noiseinduced_hearing_loss_australia_2010.pdf

Safe Work Australia. (2018). Code of Practice: Managing noise and preventing hearing loss

at work. Retrieved 1 March 2025 from https://www.safeworkaustralia.gov.au/system/files/documents/1810/model-cop-managing-noise-and-preventing-hearing-loss-at-work.pdf

Safe Work Australia. (2023a). Chapter 4: Hazardous Work, in Model Work Health and Safety Regulations. Retrieved 1 March 2025 from https://www.safeworkaustralia.gov.au/sites/default/files/2023-06/model-whs-regulations-22_may_2023.pdf

Safe Work Australia. (2023b). Insights from the Beta Occupational Hazards Dataset. Retrieved 1 March 2025 from https://data.safeworkaustralia.gov.au/sites/default/files/2023-11/Insights%20BOHD%20report_November2023.pdf

Suter, A. H. (2002). Construction noise: exposure, effects, and the potential for remediation; a review and analysis. AIHA journal, 63(6), 768-789.

Suzuki, J., Kobayashi, T., & Koga, K. (Eds.). (2012). Hearing impairment: An invisible disability how you can live with a hearing impairment. Springer Science & Business Media.

Tanna, R. J., Lin, J. W., & De Jesus, O. (2020). Sensorineural hearing loss. Statpearls Study Guide. Statpearls Publishing, Treasure Island, Florida. 

Webster, D. B., & Fay, R. R. (Eds.). (2013). The mammalian auditory pathway: neuroanatomy (Vol. 1). Springer Science & Business Media.

Williams, W., Purdy, S. C., Storey, L., Nakhla, M., & Boon, G. (2007). Towards more effective methods for changing perceptions of noise in the workplace. Safety Science, 45(4), 431-447.

Zahnert, T. (2011). The differential diagnosis of hearing loss. Deutsches ärzteblatt international, 108(25), 433.