Noise-Induced Hearing Loss (NIHL)


We experience noise and sound constantly in our daily lives, normally at safe levels. However, sound can permanently damage one's hearing when it occurs at high frequency and duration.  If noise levels are too loud, even for short periods, it can cause noise-induced hearing loss (NIHL), also called permanent threshold shift (PTS). NIHL is one of the most common work-related illnesses in Ontario. A workplace is too loud if people have to raise their voices to be heard, if they have a ringing in their ears at the end of the day, or even if they notice the car radio is louder the next morning. Workplaces that aren’t thought of as “noisy” can cause NIHL, if there are infrequent but loud impact noises. Learn more about Noise, including how to monitor sound levels and how to control noise exposure  here.

How Hearing Loss Occurs

All sound waves enters the outer ear and travel through the ear canal to the ear drum. The ear drum vibrates the 3 tiny bones in the middle ear called the malleus, incus, and stapes. These bones amplify the sound vibrations, and send them to the cochlea. The cochlea is lined with microscopic hair cells, which move in response to the sound wave. The hair cells transmits a “sound” signal to the auditory nerve.

inner ear parts
Image Source: NIDCD (U.S. National Institute on Deafness and Other Communication Disorders)

NIHL is what happens when the sound waves have caused permanent damage to the microscopic hair cells. NIHL can be caused by long-term exposures to noise or to very short-duration loud sounds called impact noise.



Raising Awareness About Noise

October 27, 2017

The Chairman of the Occupational Disease Working Group for Noise with the Intrastructure Health and Safety Association in an 8 minute clip from a presentation on the importance of addressing noise in the workplace.



Occupational Disease Action Plan (ODAP)

Occ-tober Symposium 2018

Wagish Yajaman, M.H.Sc., CIH, CRSP of Workplace Safety and Prevention Services presents a report from the Noise Working Group.

Noise-Induced Hearing Loss

Noise-induced hearing loss (NIHL) is the depletion of one’s hearing as a result of prolonged exposure to high levels of noise. When the sensitive structures of the inner ear are damaged, temporary or permanent hearing loss can occur.

Diagram showing the difference between normal and damaged hearing cells



Noise: It's Effects and Methods to Reduce Exposure

RSI Day Event 2017

Kevin Hedges presents this seminar on avoiding noise and the importance of protecting workers' hearing. Practical methods of prevention are discussed.

Methods for Prevention

The following methods can be used to reduce or control noise levels in a workplace:

  • Establish a policy that only allows for purchase of equipment that is lower than 75 decibels
  • Install vibration control (isolators, damping)
  • Use sound dampening materials for conveyors, bins (noiseless steel, plastic coatings, etc.)
  • Install silencers, mufflers, specially designed compressed air nozzles, etc.
  • Balance rotating parts, avoiding harmonic frequencies, etc.
  • Avoid impacts in process flow (e.g. slide instead of drop)
  • Install enclosures, barriers, curtains, etc.
  • Install sound absorbing acoustic wall/ceiling treatments
  • Increase the distance from the worker to the source



New System Noise Resources

October 27, 2017

The Chairman of the Occupational Disease Working Group for Noise with the Intrastructure Health and Safety Association addresses the importance of addressing noise in the workplace in a 14 minute clip from the presentation.

SOBANE Approach

A Different Approach to Solving Health and Safety Concerns

This information is based on materials produced by Jacques Malchaire (Belgium).

SOBANE is an acronym for: Screening    •    OBservation    •    ANalysis    •    Expertise.
It represents an approach to solve the workplace health and safety problem which stresses providing an appropriate level of expertise. Malchaire estimates that up to 80% of concerns can be addressed in the Screening and Observation stages.


Screening is the shop-floor level where workers and supervisor recognize hazards and deal with them directly.


OBservation is when simple assessment tools are used to evaluate the seriousness of the hazard and make recommendations for improvement. This is the Health & Safety Committee/ Representative level of expertise (a few hours of training with practical experience).


The Analysis level implies specialists with formal training in occupational hygiene and/or ergonomics.


Expertise refers to recommendations provided by experts (usually outside consultants) with highly technical knowledge to resolve particularly difficult control problems.

The philosophy behind the SOBANE approach is that the lower levels are supported by the higher levels in their practical efforts to resolve health and safety issues.

Ideally, a health and safety issue can be resolved on the shop floor, with the health and safety committee/representative and coordinators only getting involved when the shop floor parties need support. Simple determinations of whether or not some hazard needs to be addressed do not require specialists or experts. Such determinations are either quite obvious to the worker doing the job, or can be assessed using simple “rules of thumb”.

Specialists and experts are only called in for complex problems where their training and expertise is needed – when the observation level techniques require further assistance to identify, assess and control particular hazardous situations.

This information is intended to provide tools for the early stages so that workplaces can address noise concerns efficiently and recognize when they require the support of specialists and experts.

OHCOW Tools to Help Prevent Hearing Loss

Noise-Induced Hearing Loss (NIHL) Audiogram Calculation Tool

OHCOW’s Noise-Induced Hearing Loss (NIH) Audiogram Calculation Tool is a fillable pdf designed to assess values based on the worker’s audiogram to clarify if their NIHL meets the minimum requirement for establishing a NIHL claim with the Ontario Workplace Safety and Insurance Board (WSIB).

The NIHL Audiogram Calculation Tool allows anyone who has had an audiogram conducted, to input their results into the calculator to determine if those calculations fall within the criteria set out in the WSIB policy for NIHL # 16-01-04.

Download NIHL Audiogram Calculator Tool

Noise Exposure Calculator

A fillable Excel sheet developed by OHCOW, this tool can be used to calculate the following:

  • the 8 hour equivalent sound exposure level as per the equation in O.Reg 381/15.
  • the 8 hour equivalent sound exposure level for different noise levels and for specified lengths of exposure time.
  • the amount of time it takes to reach either an equivalent 8-hr exposure or Lex,8 of 85 dB(A) (in yellow) or Lex,8 of 80 dB(A) (in green).
  • roughly the amount of time it takes to reach either an equivalent 8-hr exposure (Lex,8) of 85 dB(A) or an Lex,8 of 80 dB(A).
Download Noise Exposure Calculator

Apps to Download

Below is a short list of apps from iTunes and Google Play. The list is based on reading some high quality evaluations of noise measuring cell phone apps, plus some of our own experimentation with such apps.

niosh meter icon

NIOSH Sound Level Meter

iTunes Store

An award-winning app combining the best features of professional sound level meters and noise dosimeters into a simple, easy-to-use package.



iTunes Store

A  sound level meter, iPhone/iPod/iPad compatible, and adapts itself to the actual screen resolutions ("HD", "retina")...

Noisee app


iTunes Store

An intuitive professional-grade sound level meter for iPhone and iPod touch...

SPL Meter

Google Play

Sound Pressure Level Meter. This app uses the microphone to detect sound and convert it into an SPL value.

SPLnFFT Noise Meter

iTunes Store

SPLnFFT is a sound level meter (noise meter) with frequency analyzer, frequency meter, test signal generator, dosimeter.

Open Noise app icon


Google Play

OpeNoise is a real-time noise level meter.

More Resources

Doing Something About Workplace Noise (OHCOW fact sheet):


Noise-Induced Hearing Loss (2022 slides)

Noise: Its Effects and Methods to Reduce Exposure (2014 slides)

Noise-Induced Hearing Loss Prevention (2017 slides)


Noise (2016)

Noise-Induced Hearing Loss Prevention (2015)

Noise: Its Effects and Methods to Reduce Exposure (2017)

Occ-complishment: New System Noise Resources - IHSA and OCHOW (2017)

International Noise Awareness Day (April 27, 2022):

Noise Fact Sheets (CCOHS (Canadian Centre for Occupational Health & Safety)):

A Guide to the Noise Regulation under the Occupational Health and Safety Act (Ontario Ministry of Labour, Immigration, Training and Skills Development):