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Lets say I have a low-pass filter in a sound system.

I draw a magnitude and a phase diagram as a function of the frequency.

Disregarding the magnitude, how does just the phase affect the sound we hear?

TonyM
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gamliel basha
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2 Answers2

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Most experiements I've seen reported claim no audible effect for changing the phase of different frequencies. However, there is a minority of people with 'golden ears' who will claim to be able to hear a difference. Try it yourself, and if you can't hear a difference, don't worry about it.

Neil_UK
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Think about what happens when you listen to a loudspeaker and move a little closer or a bit further away. Now sound has a wavelength that is related to the frequency of the sound and the velocity of sound in air (343 m/s). So with 1 kHz the wavelength is velocity/frequency = 343 mm. With 7 kHz the wavelength is 49 mm.

So, if you listened to 1 kHz and 7 kHz tones at some particular distance then moved you head a few mm the phase relationship between 1 kHz and 7 kHz is significantly altered but does your ear tell you something different? If what you listened to was a complex piece of music and you moved your listening position slightly would the music sound different other than maybe a bit louder or softer)?

So, with a low pass filter we instantly hear that the treble sounds have diminished but has all the various phase changes due to that filter brought about some radical reshaping of the sound other than the treble being lowered due to attenuation?

I would say not.

Andy aka
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  • so why do we need the phase graph if it doesnt effect nothing except of knowing if the system is stable or not? – gamliel basha Jun 07 '17 at 19:23
  • You are talking about sound systems. There are plenty of other applications where the phase shift is very important. – Andy aka Jun 08 '17 at 08:09
  • Andy aka, can you give me an example for an application where the phase shift is important? – gamliel basha Jun 08 '17 at 15:31
  • If you are trying to detect a pulse in the presence of noise, if you don't use the right sort of filtering, you will misshapen the pulse and find it harder to estimate the pulse width. This might be relevant to lidar or sonar applications such as on distance recognition systems on vehicles. – Andy aka Jun 09 '17 at 07:37