Speech Understanding vs. Comfort

Hearing Aids
#1

For those with severe/profound loss with the usual Recruitment problems, there is a trade-off between clarity with good speech comprehension and comfort (comfort= no blasting loud sounds). The industry standard, Wide Dynamic Range Compression does modify the speech envelope which does change the essential characteristics of speech…making it harder for the brain to comprehend.

The higher the compression ratio the less faithful the sound delivered to the patient’s ear.

Same goes for MPO (Maximum Power Output) circuits. They all modify the natural sound of speech.

Maybe, it would be better for our professional fitters to reduce compression (knee point and ratio) and encourage their patients to accept the occasional blast.

Comments? Ed

#2

Volume and speech comprehension do not necessarily go hand in hand

#3

can you make it simpler for non-native speackers.

What do you mean?

#4

Well I don’t really wish to imply that I am speaking for Ed, but to keep it simple Ed is saying that a lot of things hearing aids try to do is to try to improve speech comprehension is a noisy environment. The way to do that is through microphone direction and reducing background noise, which also, to keep it simple, reduces overall volume. So why not crank up the volume to better improve comprehension. but it doesn’t work that way. Sure cranking up the volume may help somewhat, but even in a quiet situation, if your comprehension is poor it will remain poor. Take it from someone who knows.

#5

Thanks Hask12 but I didn’t have speech in noise in mind. Cranking up the output in mixed speech and noise will not improve comprehension as you said. The S/N ratio remains the same. It most likely would decrease comprehension due to level induced distortion in the patient’s hearing system.

As requested here is a non-technical explanation of my earlier post:

For those with really poor hearing with the usual inability to comfortably handle loud sounds (Recruitment), maybe it would be better for your fitter to lower the hearing aid’s settings that make loud sounds softer (Compression). I believe that higher compression settings, though improving comfort, does reduce speech understanding because compression changes the natural loudness relationships in speech.

The same may be said for the Maximum Power Output MPO settings. Ed

#6

What do you mean by that? Do you mean fine tunning ?

#7

In one way yes. What I am saying is that there is a trade-off between comfort and speech comprehension for those with lots of recruitment.

Set the compression/knee point high and you reduce speech understanding. Conversely, set them too low and you make for discomfort and at extremes blast with attendant masking.

I suspect many professionals ere on the side of excess comfort. Ed

#8

I will not ask more questions becasue I will no understand the technical stuff.

If what you say is true, it is really a problem.

#9

Stream: No matter how you adjust the hearing aid, when you stuff natural speech which has a dynamic range (softest sound to loudest sound) of 50-60+db into a persons compromised hearing system that can only handle 10 to 30db range it means what goes into that person’s ear is not exactly what the speaker uttered.

There is a huge volume range difference between natural speech and highly compressed speech. DB, decibels, are on a log scale not a linear scale. Ed

#10

To my surprise this months Hearing Journal has a scholarly article on this subject. The author emphasises the role of compression timing in comprehension and fidelity. Also he says the Bernafon Verite is the way to go if you have lots of loundness recruitment.

He works for Bernafon. Ed

#11

Arthur Schwab has a excelent book on hearing aids, I believe he had some role
on the creation of the Channel free

#12

Compression, good or bad?

Where do your uncomfortable levels sit ?

Take 1 frequency, I dunno, say 1Khz. Your loss is 50dB. Normal speech is about 65dB - how much gain is correct?

Now take a higher input level - 90dB and apply the same level of gain. Are you suffering noise damage yet?

Linearity is great for losses with a considerable conductive element - normal sensorineural losses usually don’t get on with it at all.

#13

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