Delay time vs. features



yesterday I thought, I might want to try to swtich my noise reduction to “off”, because it was on the lowest setting anyway, and I wanted to know what it sounds like.

So I did, and while running or boiling water is louder now (though not annoyingly so), I also noticed that my sense of direction improved. As this is, of course, highly subjective, I wondered if this can be true.

Digital hearing aids add delay, delay disturbs sense of direction. Will turning off noise reduction in a digital hearing aid lessen the amount of delay that´s needed for signal processing? Has anyone ever measured?

Just curious …


Interesting question. I work with audio and signal processing on a daily basis. I have not tried measuring or determining delay times with a hearing aid. The delay is minimal in a hearing aid or open fit technology would be hated by most users…hearing the real sound and a long delay time for the amplified signal would create an echo effect. I wear open fit in my left ear and have not noticed any significant echoes or delay-like effects.



I didn´t notice any delays, either. But while it would take more than 10 ms to notice a delay, one must not forget that sound travels 342 m/s, so in a millisecond, it still travels 34 cm. So if you add just 1 ms of delay, your brain thinks that your head is 34 cm bigger … well, not exactly, but as the sense of direction is quite precise for human hearing, I guess that 1 ms of delay more or less might make a difference here, even if you don´t hear it as a delay.


My two cents:

Sense of direction is achieved by the brain using the following mechanism:

  • Phase difference: For sound waves up to 1000Hz
  • Intensity difference: For sound waves starting at 1000Hz

I don’t think that disabling noise reduction increases response time. My guess is that you are now aware of so many new things and your brain is evaluating everything. Whitin a week, you’ll become adapted to your “new” hearing and everything will return to normality.


I don´t think so, I have had hearing aids for more than half a year now.

Also I do think that if the DSP-software (I mean, the software on the hearing aid) is programmed correctly, it will of course reduce the latency to turn off certain features.

If this really has an audible effect is, of course, a different story. By the way, this is related to your other thread “how do the noise reductions work”. If you find out, you might be able to tell if noise reduction adds latency.


I suspect the issue is that interaural level diifferences are no longer disturbed since the noise reduction algorithm has been disabled bilaterally. On average this effect is somewhat small but perhaps you are rather sensitive to the effect.