13/11/2009 by John Lloyd.

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04/11/2009 by John Lloyd.

First, a quick understanding of what ’sound’ is.

Sound is a pressure wave and is the result of molecules impacting upon each other, caused for example by objects hitting each other (such as a hammer onto an anvil) or from objects vibrating (such as our vocal chords). Sound therefore requires a molecular medium to pass through, and the sound is heard until the energy fades out (this fade through air is halved every doubling of distance and is know as the inverse square law). Sound can vary in loudness and pitch.

(Note: The reason there is no sound in outer-space is because outer-space is a vacuum, and has no molecules. Sound can transfer within objects in space but this stops at the edge of the object because there is then no air to then carry the sound further).

Sound loudness is measured by the decibel scale, defined as the decibel sound pressure level (dBSPL)

When we test hearing we use ‘puretone’ sounds which are frequency specific and contain no harmonics. They are by definition ‘pure’.

Many decades ago hearing tests were carried out on several hundred young adults with anatomically healthy ears by measuring the faintest level of puretone signal each could hear, measured in dBSPL. This then gave an average minimum threshold of hearing for people with good hearing in which to measure other people against. However, the natural ear actually hears different frequencies at vastly different pressure levels - this can be shown by ’Equal Loudness Curves’ (aka Phon curves) shown here:

Note 1: This graph is based on subjective comparison of frequencies based around 1kHz. So whilst 3kHz is less than zero, it just means we can hear 3kHz better than 1kHz (due to the natural amplification characteristic of the shape of the ear) - we cannot possibly hear better than Zero dBSPL (zero sound!). The graph shows that we can hear 3kHz at a much lower sound pressure level than say 20Hz.

Note 2: As shown in the graph above, young adults with healthy ears can typically hear between 20Hz (very low pitch) to 20,000Hz (very high pitch), but as we grow older this range narrows, especially from the high frequency end. Hearing tests are typically limited between 250Hz-8000Hz being that this is the range of speech.

It would be quite confusing to use a graph like this to base every other test upon, so a flat graph called an Audiogram was produced (shown below). This shows the threshold of sound to be ‘zero decibel hearing level’ (dBHL) - defined as the average minimum level of sound which an 18 year old with anatomically healthy ears can here - and this average perfect is what we compare ALL hearing tests to (note it is possible to hear better than 0dBHL, as it is an average figure). The graph also shows the average upper threshold of hearing where sounds are considered uncomfortable (but not painful) - which is on average 120dBHL. (Note: the graph is always upside down to represent a loss).

Hearing test results can vary wildly, but most people suffer from high frequency loss caused by hair cell damage in the cochlear (the inner ear / nerve centre).

A typical test result is shown below, on an Audiogram which also shows where typical speech sounds occur.

This audiogram shows a client with good low frequency hearing and mild to moderate high frequency hearing loss.

The circle on the left shows that the client is hearing louder vowels sounds normally, but the circle on the left shows they are missing the quieter consonant sounds, which are needed for clarity of speech. This client will therefore perceive that people are not speaking clearly - a clear sign of early stage hearing loss.

I hope this helps! - Please do add comments or ask questions.

For an explanation of the hearing test procedure click here.

All the best

John

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01/11/2009 by John Lloyd.

And finally, Phonak have completed their portfolio upgrade with the new Phonak Milo.

An entry level hearing aid incorporating advanced features such as adaptive dual microphones and noise reduction based around the CORE processing platform that the more advanced range is built on.

So even at a budget level we can now provide fantastic hearing solutions as custom in-the-ear models or mini-behind-the-ear models.

More information here

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01/11/2009 by John Lloyd.

To compliment the Audeo Mini we are also please to announce the arrival of the new Phonak Audeo Smart.

The Phonak Smart effectively replaces the Audeo YES incorporating the same housing improvements whilst also being wireless functional and therefore compatible with the iCom and the MyPilot, and also now includes the brilliant DuoPhone (an article on DuoPhone is listed under ‘accessories’).

The other main addition is the push button located between the dual microphones which can now be used for mulitple programmes OR for a volume control (more information available on request).

Having smoothed out the minor housing issues that some people experienced this aid is now arguably the best RIC currently available and with Bluetooth functionality it is probably the most versatile.

Full features and colours here

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01/11/2009 by John Lloyd.

Phonak have just added to their portfolio with the new ‘Audeo Mini’.

A miniature version of the already massively successful Audeo YES which includes all the technology of the three previous technology levels (the 3, 5 and 9) but with a few improvedents including:

1. Hydrophobic microphone protection preventing dust and moisture ingress, which will reduce repair needs.

2. An improved sliding pin mechanism for removing and replacing the speaker wire which the client can now easily do. This is great for field dispensers and clients alike, as it means the client does not have to wait to see someone if their is a fault, as long as they have a spare speaker wire for each ear.

3. Radical new lightweight design - The Audeo Mini is the smallest receiver-in-the canal hearing aid currently available, being 10% less overall volume than the Widex Passion (although the Passion is remote control compatible).

4. Improved battery door, to prevent batteries falling out.

5. Nano-coated housing to prevent moisture ingress.

Note: The Audeo Mini has no wireless function and therefore is not iCom or MyPilot compatible.

Features and colours shown here

Who is this aid for? People who want the highest performing and most discreet RIC hearing aid with no add-ons. Easy to use, fully automatic and does exactly what it says on the tin.

Click here to see the Phonak video of the new Audeo Mini

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