Thursday, February 20, 2014

Sound Sensitivity

Written by Courtney Morrison, Clinical Audiologist

The human ear is remarkably sensitive to a huge range of sound levels. For example, the sound generated by a jet engine, at 120 decibels, is a trillion times more intense than the sound level at the threshold of hearing and the intensity of a normal conversation can be 10 000 times greater than that of a whisper.  With hearing loss, hearing thresholds increase and soft, low-intensity sounds become inaudible. However, for some individuals, both with and without hearing loss, everyday noises can seem intolerably loud. Why is this?

Intensity Level
Greater Than
Threshold Of Hearing
Threshold of hearing (TOH)
0 dB
Rustling leaves
10 dB
20 dB
Normal conversation
60 dB
Busy street traffic
70 dB
Vacuum cleaner
80 dB
Large orchestra
98 dB
Front row of rock concert
110 dB
Gun shot at close range
140 dB

What is hyperacusis?
Þ hyper–  above; excessive
–acusis,  hearing

Hyperacusis is an unusually low tolerance to everyday sounds which are tolerable for most listeners. Individuals who experience hyperacusis often try to avoid sounds or environments that they perceive to be too loud, or will grimace or cover their ears when they encounter them. There are estimates that 40-86% of people who report this also report tinnitus and while it often accompanies a damaged auditory system many sufferers present with no obvious hearing loss.

While there is no conclusive evidence as to what causes hyperacusis, it has been suggested that it is related to neurotransmitter activity in the brain, and is influenced by stress, anxiety and fatigue, not unlike tinnitus.

What is recruitment?
A large increase in the sensation of loudness with only a slight increase in the actual intensity of sound is what is known as recruitment. If you’ve ever tried to get the attention of someone with a hearing loss a couple of times at your normal speaking level, before raising your voice to a somewhat louder volume, and been met with the response “no need to yell, son” you have experienced hearing recruitment. Recruitment is associated with sensorineural, or inner ear hair cell damage. At some decibel level of sound, functional hair cells adjacent to the damaged hair cells kick in, or are recruited, resulting in a sudden boost in the perceived loudness of the sound.

What can be done to manage hyperacusis and recruitment?
Today’s hearing aids have a feature called Wide Dynamic Range Compression (WDRC) which is designed to make soft sounds audible, and loud sounds tolerable, meaning it works great for individuals with recruitment.

For patients with hyperacusis, often the first instinct is to protect their ears with plugs, muffs or other devices. Constant use of ear plugs, however, can have the adverse effect, accentuating the loudness of the environment when the plugs are removed.  Instead, the approach increasingly recommended by hearing professionals is to desensitize the ears using noise stimulation, in much the same way you would use a noise masker or sound therapy for tinnitus, and to counsel the patient following a thorough history-taking and audiological assessment.

Wednesday, January 29, 2014

Advanced Signal Processing in Today’s Hearing Aids

Written by Courtney Morrison, M.Cl.Sc.

Today’s hearing aids have come a long way from the big beige bananas that may first come to mind.  Not only do they amplify sound, they work to enhance meaningful signals (i.e. speech) in order to compensate for a damaged auditory system. When you realize how much your little hearing aid is actually doing second by second, you may find you have a new appreciation for the tiny battery that keeps it going for 100 hours or more!

Acoustic Environment Classification
Almost any new hearing aid you will try is constantly analyzing the sounds around you in order to classify the listening environment into one several categories. More basic hearing aids are generally determining between a ‘quiet’ or a ‘speech in noise’ environment, whereas more advanced hearing aids are often sorting the incoming signal between quiet, speech in noise, noise alone and music categories.
The hearing aid makes this classification based on various characteristics of the incoming sound including the overall level and the frequency and variations in amplitude of the sound waves that are picked up at the microphones.

By classifying the acoustic environment, the hearing aid can then automatically enable or disable other features which reduce noise and are designed to make speech audible and understandable.

Noise Reduction
One of the main goals of signal processing in hearing aids is to make listening comfortable and noise less bothersome. Imagine sitting in a café, in conversation with a friend, when suddenly the loud humming sound of a blender cuts in. Your hearing aid detects this hum, determines it is an unwanted sound and then uses an algorithm to reduce the noise. Many of today’s hearing aids can reduce noise levels by up to 10 dB! Noise attenuation is particularly effective for what we call ‘steady-state’ sounds – think of the fairly constant sounds from fans, refrigerators or vacuum cleaners.  Studies have shown that noise reduction techniques employed in hearing aids improve listening comfort, reduce listening effort and offer preferred signal quality for hearing aid users.

Directional (Beam-forming) Microphones
One of the biggest issues for new hearing aid users is that unwanted and distracting background sounds are amplified, along with the things that you are trying to hear.  Directional microphones have been proven to improve speech understanding in noise, reducing some of the background noise, thereby boosting the signal-to-noise- ratio (SNR). They work by changing the direction of microphone sensitivity, generally making the microphones more responsive to sounds coming from the front and less responsive to sounds from the sides and rear. Essentially, they act like a spotlight, directing the focus to the front and minimizing other distractions from your surroundings.
Imagine you are in the café when several groups of people enter and sit at tables nearby. In this case, the background noise that is interfering with your ability to communicate with your friend is the babble and chatter coming from the people around you. Noise reduction as discussed above is likely to be less effective in this case, as the babble of speech is much more dynamic then steady-state sounds; however, the directional microphones of the hearing aid have kicked in and are now focusing their beam of sensitivity towards your friend sitting across from you, and dampening sensitivity to the noisy table behind you.

Feedback Cancellation
At one time or another, you have likely heard a whistling hearing aid, perhaps from the person sitting next to you in church or when you’ve gone in to hug your great-aunt Myrna. That whistling sound, termed feedback, occurs when amplified sounds leak out around a hearing aid and are then picked up by the microphone and re-amplified. Having a properly fitted earmold or custom aid is the first step in ensuring feedback is minimized; however, advanced hearing aids also use various algorithms to stop the whistling quickly or before it occurs. As with most digital processing strategies, exactly how and when this is done varies between hearing aid manufacturers. Certain adaptive feedback managers will generate a sound wave opposite to that of the whistle, essentially cancelling it out, while others will change the output frequency slightly so that it is no longer troublesome. These advances in digital feedback management have allowed receiver-in-canal (RIC) style aids to be possible!

This is just some of the advanced digital processing that goes on inside of hearing aids. Other notable technologies include frequency compression, frequency lowering, wind noise and impulse noise reduction. Certainly there is a lot more going on in today’s tiny hearing aids than meets the eye!

Wednesday, January 8, 2014

Noise Induced Hearing Loss

Written by: Kelsey Spurrell, Clinical Audiologist

We all know that working in a loud environment can impact your hearing. However few people actually understand the impacts of noise induced hearing loss.

Hearing loss can be caused naturally with age but this doesn’t ordinarily happen until later in life. If you are experiencing hearing loss earlier and have been exposed to loud sounds, it is more than likely noise induced. NIHL (noise induced hearing loss) is caused by two factors working together: the INTENSITY of the noise and the LENGTH OF TIME a person is exposed to it. Repeated exposure in combination with these two factors gradually produces NIHL a form of SNHL (sensorineural hearing loss). SNHL is permanent and this is due to the death of hair cells within the inner ear.

NIHL normally presents itself as a high frequency hearing loss. This means that high pitched sounds, such as the /t/, /k/, /s/ sounds in speech, become more difficult to hear. This results in the perception of muffled speech. Other common symptoms of NIHL are tinnitus (ringing in the ears), the inability to understand speech, and difficulty following conversations when there is background noise. It’s important to know that NIHL can progress over time, and can eventually impact low pitched sounds, such as vowel sounds in speech.

But what is noise? Noise is any loud unwanted sounds. In fact, anything that is 85 dBA or more is considered dangerously loud. For instance, a lawn mower, motorcycle, jackhammer, and even a blow dryer can all produce sounds that can cause hearing loss.

The cause of NIHL may be most often work related, but the effects are felt far beyond the workplace. According to a 2000 Board of Health Report to the City of Toronto: there is evidence indicating that noise can effect general health, which include but are not limited to an increased risk for cardiovascular disease, chronic fatigue, and damages to mental health such as anger and anxiety. The report also states that “more people are affected by noise exposure than any other environmental stressor.”

While there are a variety of negative side effects associated with NIHL, it is somewhat preventable. It`s your duty and your right to protect yourself from any dangers in the workplace.


Noise level exposure is regulated by both federal and provincial legislatures. Occupational exposure limits for noise can be described as the maximum duration of exposure based on different levels of noise. Two important factors for calculating this are the criterion level and the exchange rate. The criterion level is defined as the level of noise permitted for an 8 hour work shift. In N.B., regulations state the criterion level to be 85 dBA, that’s the level of a power drill. The exchange rate states that when the noise levels increase, exposure to the noise must decrease. In N.B., regulations define the exchange rate to be 3 dBA. So for every 3 dBA increase in noise level, the exposure time must be reduced by half. This means if the noise level at your workplace increased to 88 dBA then you should only be exposed for 4 hours!!

To protect your hearing, try to stay away from the source of the loud noise but most importantly use hearing protective devices. A variety of these exist including foam ear plugs, custom ear plugs and ear muffs.

The following infographic provides a great loudness scale for reference:

Friday, November 8, 2013

Hunting & Hearing Health

Written by Courtney Morrison, Audiologist 

It’s that time of year again, when many folks around New Brunswick don camouflage and orange and take to the woods.

Many hunters do not realize the importance of protecting their hearing while hunting. Most firearms produce noise greater than 140 decibels (dB), with larger rifles producing up to 175 dB. For comparison, conversational speech is generally 65 dB and lawn mowers and snowblowers are approximately 106 dB. A single exposure to the level of noise produced by a firearm can be enough to permanently damage your hearing system.

Hearing loss resulting from excessive noise is generally permanent and high-pitched in nature. Individuals with this type of loss have trouble hearing certain sounds of speech, making it less clear, muffled or mumbled. Noise-induced hearing loss is often accompanied by a high-pitched and constant tinnitus which can be very bothersome for some people.

In hunters, it is common to find the hearing in one ear is worse than the other. In right-handed shooters, the left ear is closer to the barrel of the gun and often suffers the most damage, as the head provides a somewhat protective effect.

Hearing is an important sense when hunting; luckily there are types of hearing protection available that can prevent damage from loud impulse noises, while still allowing you to hear the rustling of leaves and other non-damaging sounds. 

Electronic hearing protection devices amplify soft ambient sounds from the environment but shut off when there is a loud noise. They are most readily available in the form of earmuffs and start at approximately $50.

Non-linear hearing protection devices are non-electronic and can be custom made for your ears. A filter inside the custom mold or earplug allows soft sounds to pass through, but blocks out loud sounds over a certain noise level. Custom-made non-linear devices are $120 and can be ordered from your audiologist.

Prevention of noise-induced hearing loss, particularly related to recreational noise exposure, has recently become of great interest to me. Although he is only in his early 20s, my brother has the beginning signs of noise-induced hearing loss. A ringing noise in his left ear led him to have his hearing tested where it was found he has a dip in his hearing at 4 kHz; the characteristic “noise notch”. He has since become much more conscious of his hearing and routinely uses his electronic earmuffs when he is hunting or target-shooting; protecting his ears and keeping his audiologist-sister happy. 

Thursday, August 15, 2013

Self Improvement & Hearing Awareness - by Jennifer Menchenton

These days it seems like everyone is interested in self improvement, and this is a good thing. Most people are trying to eat better, exercise more, and take care of themselves to live healthier more active lives. Society as a whole is on a “self-improvement” band-wagon right now, and this is spilling over into many avenues. People want to look their best, so in addition to eating well and exercising, we see an increase in adults wearing braces in an effort to give themselves a better smile and appearance; plastic surgery is even becoming more commonplace as a means of “self improvement”. People also want to perform their best at whichever activity or past time they participate in. From golf lessons to dance instruction, people are looking for new ways to enrich their lives and improve their skill. Self-improvement is a great new trend, as people are trying to be their best, and live their best lives. Just as people are aiming to improve their appearance and skill, so too should an effort be made to improve communication.
            As mentioned before in previous articles, communication is a two way street that involves both talking and listening. Listening is a skill in and of itself, and few people are truly great listeners. An essential component to listening is of course hearing. Few people actually take the time to question their hearing ability, until they develop a significant hearing loss. But how do we know if our hearing is affected unless we have it assessed? Hearing is a sense that we use everyday, and even as it begins to decline, we can still use it in a somewhat effective fashion by asking people to repeat themselves, getting closer to the sound, or turning up the volume. These are strategies we use to compensate for difficulty hearing, without thinking twice that there may be an underlying hearing loss present. In some situations it may be normal to have difficulty hearing someone, for example in a crowded restaurant. However if you are having trouble hearing in a fairly quiet situation, it may be a sign that your hearing is on the decline. In any case, if you are not having your hearing assessed, you have no way of knowing if you are actually hearing at your best ability.
            I’ll use the analogy of going to the dentist. Many people will go to the dentist at least once a year for a check up. On some occasions, the dentist may tell you that you have a cavity that needs to be filled. This may come as a surprise, as you were not getting any symptoms or having any problems with your teeth. Usually you will take the dentists advice, and have the cavity filled. If you had not kept your annual appointment with the dentist, the cavity would not have been detected, and probably would have continued to get worse and eventually become quite bothersome and painful. The same is true for your hearing. If you do not have your hearing checked on a regular basis, how can you really know that you are hearing and performing at your best? The truth is there is no way to know, unless you have it professionally assessed. Hearing loss begins so gradually that many people will go years, waiting until it has started to make a very negative impact on their lives before doing anything about it. The trouble with this is, the longer you wait to seek help with your hearing the more challenging it will be to get improvement in the future. Hearing is a sense that needs to be actively used, and unfortunately “if you don’t use it, you lose it”.
            Hearing assistance does not necessarily mean hearing aids or devices. If you are monitoring your hearing on a regular basis, and a mild hearing change is detected, the audiologist can provide you with communication tools and strategies to improve your current hearing needs. An audiologist receives a wealth of training on both hearing aids as well as hearing rehabilitation, and can provide you with tools to truly hear your best. In an age of self-improvement, looking your best, and performing your best, it is really surprising how many people will refuse or ignore the importance of good hearing. I feel that if you really want to be your best, you must strive for your absolute best hearing. Audiocorp has three full time audiologists and offers complimentary hearing checks. If you are striving to be and hear your best, we would love to help you reach your goals.