More Hearing Articles

Binaural streaming for telephones
We love to keep you up to date with new developments in hearing aids, and we think this is something worth telling you about. For those of you who struggle to hear on the telephone, this might be just the help you need.

Hearing aid developers have created a new feature where a hearing aid has something like a broadband connection that operates wirelessly between the hearing instruments. So, a message that is sent to one hearing aid microphone, can be sent by this wireless network, to the other hearing aid. It is beneficial for telephone use, as this system allows the hearing aid wearer to put the telephone to one ear, but to hear the conversation in both hearing aids!

It is also useful in other situations, like in the car. If you were a passenger, for example, you could tell your hearing aid that you were interested in the signal from your right hearing aid, and that stronger signal of the speech of the driver would be transmitted to both hearing aids, while the road noise on the left would be ignored.

These features are generally only available in recent higher end products, and need a remote to access them. If you have a new high end hearing aid, it is possible that this feature is available in your hearing aid, but not enabled. If you’re not sure about whether you have this feature in your hearing aid, please give us a call and we can let you know.

This is the beginning of a series of articles “getting to know your hearing instruments – inside and out”.

Signal processing in hearing aids
Signal processing can be described as what happens inside a hearing aid after a sound has been detected by the microphone, and before it is delivered to the receiver (or loudspeaker).

You may have heard of analogue and digital hearing aids and wondered what that really meant. In basic terminology, the difference between the two is whether the signal processing is carried out by electrical components or by digital signal processing. The difference could be likened to a stereo that has simply a bass and treble to adjust the sound (analogue aid), or whether it has a graphic equaliser where many components of the sound can be changed (digital aid).

Analogue Signal Processing
In an analogue hearing aid the signal received by the microphone is modified by electrical components such as capacitors and resistors before passing to the amplifier and being heard by the wearer.

Audiologists controlled the output of these hearing aids with a small screwdriver that turned a trim-pot. The adjustments were limited to perhaps how much low or high frequency power was relayed to the client, and in some, the maximum output of the hearing aid. Analogue sound is like receiving a photocopy, and it causes deterioration of the original signal.

Digital Signal Processing
In a digital hearing aid, the sound still has to go through the electrical components of the microphone and the amplifier, but the way in which the signal processing is carried out is digital. Once the sound is received by the microphone it passes to an analogue to digital converter. This means that the analogue sound wave is converted into a digital signal, ie 1’s and 0’s. Once the signal is digital, it is processed, the passes through a digital to analogue converter, onto the amplifier, and then is heard.

Depending upon the hearing aid, the digital signal is broken up into a number of frequency bands. In each of these bands a number of changes can be made to the digital signal. So, for example, in one of perhaps 20 bands a signal can be modified to provide different outputs for soft, medium, and loud sounds! It can also be told to respond differently depending upon the sounds present in adjacent bands. A typical digital hearing aid is really a very sophisticated and miniature computer that makes millions of processing decisions every second, and still delivers a sound that appears to be in real time.

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Microphone directionality in hearing aids
A microphone is an essential component in all hearing aids. It picks up sound from within the environment and converts it to an electrical signal which can then be processed by the hearing aid. You may have heard that it is best to have directional hearing aids, and this article aims to explain what directionality is, and why it will benefit you.

What are directional microphones?
While audiologists often refer to hearing aids as being omnidirectional or directional, this generally refers not to the microphones themselves, but to the method in which the hearing aid is able to process sound.

The fact is that almost all modern hearing aids have only omnidirectional microphones (omnidirectional means that the microphone is able to receive signals equally from every direction), but it is whether there is one microphone or two that dictates whether a hearing aid is considered directional.

In a hearing aid with two omnidirectional) microphones, the microphones are lined up a very precise distance apart, and the hearing aid is able to detect which direction a sound is coming from by the timing differences of a particular sound reaching each of the two microphones. So, a sound that is behind a person will be received by the back microphone before it is detected by the front microphone. In this way the two microphones can work together to ‘beam form’. That is, based on a set of criteria, they can minimise the impact of sounds coming predominantly behind (the ‘null point’), while preferentially amplifying sounds coming from in front of the wearer.

Sounds simple? Well, now we’re ready to deal with the type of directionality – fixed or adaptive. A fixed directional hearing instrument will have a beam which has a fixed shape and size. When this hearing aid is working directionally, all sounds within the beam will be amplified, while all sounds outside the beam will be damped. On the other hand, an adaptive directional hearing instrument has a beam that changes the location of the null point (and therefore the shape of the directional response) depending upon the location of the dominant noise source around the head. This added level of sophistication has the advantage of greater effectiveness at reducing annoying and disruptive noise sources compared with a static of fixed null point.

Then we need to consider channels. A fixed directional hearing instrument will damp sounds outside its beam in all channels (for all pitches of sound). On the other hand, an adaptive directional hearing aid will not only have a ‘roving’ null point, it can have a number of channels (from three to 33), and in each channel the null point is directed at the loudest intruding sound to be damped down.

Finally, when does the hearing aid work in directional mode? Some hearing aids work in directional mode only when you tell them to (mostly with a button on the aid or a remote control), while more sophisticated instruments will automatically switch from omnidirectional mode to automatic mode when the presence of background noise is detected.

In what ways does directionality benefit me?
Directionality in a hearing instrument will have no benefit in quiet situations, where the presence of background noise is not an issue. In noisy situations the directional hearing instrument comes into its own by providing benefits in speech intelligibility, and of listening comfort, over an omnidirectional hearing aid. In fact, studies have shown that some people wearing two directional hearing instruments in a noisy situation will hear almost as well as a normal hearing person!*

It is important, however, to remember that a hearing aid cannot determine what you consider to be relevant, and what you consider to be noise - especially if both are speech! Instead, the hearingaaid assumes that the signal in front of you is the signal you wish to hear. For this reason, when using hearing aids in directional mode, you will hear much better if you face the person you are listening to and keep as much of the background noise behind you.

In general, the hearing aid with the best signal processing and automatic operation and most channels with adaptive directionality will allow you to hear best in the presence of background noise. But ask your audiologist which one is the best match to your typical listening situations.

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Cerumen impaction
Although cerumen (ear wax) impaction was discussed in an earlier issue of our newsletter, it remains a popular topic in the clinic. As we frequently answer questions on wax build-up, we thought it was time for some revision.

Ear wax is a normal and healthy part of the ear. Everyone makes ear wax, however some people make more than others. Ear wax traps particles of dust and dirt that may enter your ear canal, and also repels water, protecting our ear drum from damage. Wax is gradually moved out of the ear by tiny hair follicles that line the ear canal, removing dirt and debris trapped with it.

If too much wax is produced it can block the ear, however it is more common that the ear becomes blocked due to improper ear care and cleaning. Cotton swabs, pencils, fingers and other objects put into the ear canal can force the wax to be pushed further into the ear and compressed against the ear drum. This is called cerumen impaction and is one of the most common causes of temporary hearing loss. It can also be caused from wearing a hearing aid, particularly an in-the-ear hearing aid. This is due to the aid blocking the ear canal, and also possibly pushing the wax deeper into the canal.

Cerumen impaction often feels as if the ear is full or blocked. It can cause hearing loss, earache and occasionally tinnitus.

Recommended treatment
To treat wax blockage, it is recommended to have it suctioned by an Ear Nurse Specialist or an Ear Nose and Throat Specialist. Syringing, using pressurized water, is no longer the preferred method, as it creates pressure against the eardrum.

Some people choose to purchase over-the-counter ear wax remover from the chemist. However, impacted wax may be difficult to remove using this procedure. Remember that an audiologist, nurse or doctor can use an otoscope to look in your ears if you are unsure.

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Ménière’s Disease
There are many different causes of hearing loss, ranging from presbyacusis (aging changes) to middle ear disease (for example perforations of the eardrum). In a previous issue of our newsletter we discussed otosclerosis, the abnormal growth of bone in the middle ear. Outlined below is an article on another cause of hearing loss, Ménière’s Disease.

Ménière’s disease is a problem with the fluid balance regulating system in the inner ear. The exact cause of the disease remains unknown. It most commonly affects people in their 40’s and 50’s, although individuals from 20 onwards may be affected. It is rarely, though occasionally reported in children. Males and females appear to show a similar incidence.

Symptoms include:
• Periodic episodes of rotatory vertigo or dizziness
• Fluctuating, progressive, low-frequency hearing loss
• Tinnitus
• A sensation of "fullness" or pressure in the ear

The initial symptoms of periodic attacks of vertigo are the most disruptive. Typically, vertigo occurs in the form of a series of attacks over a period of weeks or months, interspersed by periods of remission of variable duration. The onset of vertigo may be preceded by a sensation of fullness or pressure in the ear, increased hearing loss and tinnitus.

The hearing loss usually affects one ear, which typically loses sensitivity to low-frequency (bass) sounds the most. As well as being harder to hear, sounds may appear "tinny" or distorted. Loud sounds may cause more discomfort than normal (loudness intolerance). The hearing loss fluctuates over time. Sometimes the hearing may recover to some extent, but then on other days hearing may be difficult. In addition, the degree of hearing loss may get progressively worse with time, eventually affecting all sound frequencies.

Tinnitus is sustained, loud "ringing" in the ears. Many individuals with normal hearing experience brief episodes of tinnitus, such as a loud "ping" which declines over a period of seconds to minutes. The tinnitus experienced by Ménière’s patients is continual and does not abate with time, although its intensity may vary. In addition, it may be heard more as a load roaring or buzzing sensation, rather than a whistling.

The feeling of “fullness” in the ear is similar to that experienced by barometric pressure changes (such as when riding up or down a hill, or ascending or descending in an airplane). However, this fullness cannot be cleared by swallowing, as in the case of pressure changes. The theory is that the above symptoms are caused by an imbalance in the pressure of the fluids between two chambers in the inner ear. One chamber is thought to build up excess fluid and pressure, which causes the symptoms of pressure, increased tinnitus and worsened hearing. Eventually sufficient pressure causes the thin membrane between the chambers to rupture, and then the chemically different fluids mix, causing a severe Ménière’s attack. Following the rupture the membrane repairs itself, and it is believed that this is when the symptoms abate.

The diagnosis of Ménière’s disease is complex but usually involves excluding other possible sources of the vertigo. A thorough history and examination by an Ear Nose and Throat Specialist is essential. Treatment of Ménière’s can be with medication that reduces fluid retention, or that suppresses the sensitivity of the balance system, though they are not effective in every case. In severe cases, where oral medication is not sufficient, surgical measures may be taken. In general the symptoms of Ménière’s lessen with time, as the hearing loss plateaus.

For further information on Ménière’s Disease, the following website is excellent: www.audiologynet.com

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Restaurants in Auckland where are the places to be and to be heard
Many of our clients experience difficulty hearing their friends and family in restaurants, bars and cafes. Contemporary trends in architecture and design have led to restaurants becoming noisier than ever before. Interior designs with an emphasis on hard surfaces such as wood, metal and glass, give rise to excessive reverberation, which in turn leads to speech becoming more difficult to understand.

High reverberation levels, coupled with background music, the clamour of plates and cutlery and the grind of coffee machines have pushed the average noise level in restaurants and cafes to around 80dBA, extending up to 110dBA in some restaurants. This is significant given the noise level expected from a busy, loud street or even a lawnmower is around 85-90dBA and noise from power tools falls between 90-100dBA.

Our hearing is most sensitive to conversational speech at levels of 48-72dBA! To address this problem, the National Foundation of the Deaf (NFD) and the NZ Acoustical Society recently invited people to participate in a survey rating the noise level in restaurants throughout New Zealand. At present, there are ratings for approximately 50 restaurants and cafes in Auckland. Each of the restaurants listed has been given a star rating between one and five. One star indicates that “lip-reading would be an advantage” and five stars indicates this restaurant is “the place to be and be heard”.

If you feel that the noise level at your local restaurant is affecting your appetite, we strongly recommend that you look for a five star acoustically rated restaurant. You can do this via the NZ Acoustical Society website: www.acoustics.ac.nz or by asking Debbie or Charmaine at Russell Hearing Services to send you a copy. You can also have your say and rate the restaurants and cafes you visit by either downloading the CRAI (Café and Restaurant Rating Index) from the above website or requesting a copy from us.

Bon Appetit!

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Otosclerosis
Otosclerosis is the abnormal growth of bone in the middle ear. It usually affects the stapes bone, which rests in the entrance to the inner ear (the oval window). As the disease progresses, the stapes becomes fixated in the oval window and this interferes with sound waves passing to the inner ear. Less frequently, otosclerosis can also damage the sensory cells of the inner ear causing a sensorineural hearing loss.

The cause of otosclerosis is not fully understood although research has shown that it may be hereditary. On average, a person who has one parent with otosclerosis has a 25 percent chance of developing the disorder. If both parents have otosclerosis, the risk goes up to 50 percent. Research shows that white, middle-aged women are most at risk.

A very gradual hearing loss is the most common symptom of otosclerosis. In addition to hearing loss, some people also experience dizziness, balance or tinnitus (ringing in the ears in the absence of an external stimulus).

Otosclerosis is treated either by surgery or fitting hearing aids. In many cases, surgery is possible through an operation called a stapedectomy. A surgeon (otolaryngologist or otologist) bypasses the diseased bone with a prosthetic device that allows sound waves to be passed to the inner ear. In rare cases, surgery can worsen the hearing loss.

If surgery is not an option a properly fitted hearing aid may help some people with otosclerosis. A hearing aid is designed to compensate for a hearing loss by amplifying sound. An audiologist can discuss the various types of hearing aids available and make a recommendation based on the specific needs of an individual.

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Generally, specialists distinguish between subjective and objective tinnitus. Objective tinnitus is a tangible noise, which is audible to the patient experiencing tinnitus as well as the person examining the patient. Your audiologist will refer you to a specialist if you have objective tinnitus, as there may be an underlying cause of the tinnitus warranting further investigation.

Subjective tinnitus, (hereafter referred to as tinnitus) on the other hand, is thought to be an intrinsically generated sound. Many tinnitus sufferers describe the sound as an aversive or a disruptive noise or tone. It is one of the most commonly occurring disorders affecting the auditory system, with approximately 20% of the population at large being affected, increasing to 33% in the elderly. While most people are not bothered by the presence of tinnitus, approximately one in four of those affected seek help.

For the majority of people, tinnitus is accompanied by a hearing loss. Most cases of chronic tinnitus are associated with a noise induced hearing loss, due to excessive exposure to industrial or recreational noise, or presbyacusis, which is the hearing loss associated with the aging process. Some pharmaceutical drugs are also associated with the onset of tinnitus. Although there is no ‘cure’ for tinnitus, there are treatments that aim to reduce the impact of tinnitus on the person’s life.

The use of hearing aids has been a mainstay of tinnitus treatments for some time. It is estimated that up to 90% of people with tinnitus may benefit from hearing aids. Hearing aids amplify ambient noises in the everyday environment, and these sounds help to ‘mask’ the tinnitus, making it less noticeable. Because many people with tinnitus have a hearing loss, hearing aids also may benefit tinnitus sufferers by reducing stress and strain.

If you experience tinnitus and would like to know more, please visit our website where you will find further information, and links to some useful sites. Alternatively, make an appointment to see Emma Towns.

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