The purpose of the demonstration is to subjectively evaluate the performance of one or more hearing instruments. The features we are trying to compare are noise reduction and directionality as normal hearing persons should be able to appreciate their relative effectiveness. The recommended noise source to be used is speech babble as it more closely matches real life background noise.

Instrument set up

In order to achieve a fair comparison, it is important to programme the aids in the same manner. All aids should be programmed to 15dB linear gain. If you intend to listen to the aids through a stetoclip rather than headphones then it may be worth increasing the gain to 20dB. The reason we have chosen a linear setting is that we are not trying to compare compression strategies so we want to take that variable away. It is not necessary to enter an audiogram as we will be changing the individual gain values. Any settings such as acclimatisation, experience level or programme type are irrelevant as the gain, compression and settings will be manually changed

Danalogic 6

Programme 1 – 15dB linear gain and omni directional

Adjust gain for all values to 15dB – this will take off the compression and make the aid linear. MPO settings should be around 100dB or higher. Set the noise reduction to “none” and enhanced adaptive directionality to “none”.

Programme 2 – 15dB linear gain and adaptive directionality

As above but switch enhanced adaptive directionality “on”

Programme 3 – 15dB linear gain, adaptive directionality and noise reduction

As programme 2 but with noise reduction “on”

Spirit 3

Programme 1 – 15dB linear gain and omni directional

Adjust gain for all values to 15dB – this will take off the compression and make the aid linear. MPO settings should be around 100dB or higher. Set the noise management to “off” and directionality to “surround”

Programme 2 – 15dB linear gain and adaptive directionality

As above but set the directionality to “full dir (adaptive)”

Programme 3 – 15dB linear gain, adaptive directionality and noise reduction

As above but set the noise management to “on”

Demonstration

Connect the output of one of the aids to a stetoclip or small microphone. If possible, attach the aid to a KEMAR or other head shaped object (perhaps even a real head) for a more realistic appraisal. If none of these are available then just hold the aid in your hand. Have the aid pointing towards you and test the sound level by speaking. Play the noise sound file through a hand held small speaker and adjust the sound level of the speaker accordingly. Experiment with the aid in different programmes and with the noise source in different positions.

Download and listen to the sound clip

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Babble.mp3 (mp3 6.26 MB)