Re: Reverb and Cancellation


Subject: Re: Reverb and Cancellation
From: Jay Smalridge (inadaze@mac.com)
Date: Mon Aug 09 2004 - 15:14:56 EDT


Okay, I understand. The point is that it is not the phase that is being cancelled, it is the amplitude that is being cancelled caused by the phase difference. It's sort of like the word peanut. It is neither a "pea" nor a "nut". Discuss!

Seriously though, it is important to understand the meaning of what I am saying, so thanks!

Jay
 
On Monday, August 09, 2004, at 11:52AM, Philippe-Aubert Gauthier <Philippe-Aubert.Gauthier@USherbrooke.ca> wrote:

>In french we use to say "amplitude cancellation by phase displacement" (literal
>translation). In fact, there is an effect : the amplitude goes to zero (or is
>partly reduced) and a cause : phase displacement (or a time delay) ... or, more
>often, we say destructive interference. Of course, everybody understand what we
>mean while we speak of "phase cancellation" (even in french, "annulation de
>phase" is surely used, but its not describing the precise thing), the problem
>is that there is no cancellation of phase, but of amplitude.
>
>Maybay, Its quite well understood and often formulated like this in english, but
>I am not able to find any translation from "phase cancellation" to french using
>the technological dictionnary of the french language office. A dictionnay which
>is quite impressive and very precise, at least in terms of science and
>techniques.
>
>Maybay I am just too crazy with specific terms?!
>
>I hope this help,
>
>Selon Jay Smalridge <inadaze@mac.com>:
>
>> Thanks for your answer,
>> I was just curious as to what other meaning of phase cancellation, besides
>> destructive interference, there could be? Just want to make sure I am using
>> the term properly.
>>
>> Thanks
>> Jay
>> On Monday, August 09, 2004, at 07:02AM, Philippe-Aubert Gauthier
>> <Philippe-Aubert.Gauthier@USherbrooke.ca> wrote:
>>
>> >Assuming that by "phase cancellation" you mean destructive interference
>> (like a
>> >sine wave plus a similar sine wave out of phase gives zero), the answer is
>> yes:
>> >Some strong delays (like early reflections) will cause some dips in your
>> >frequency spectrum. Its the same for reverberation, but in this case, the
>> >reflection arrival are so dense (in time) that the frequency spectrum
>> >alteration is more smooth. You will get a phase cancellation (partial
>> >destructive interference) when your delay is corresponding to half a period
>> of
>> >the killed frequency.
>> >
>> >This is rougly speaking. You can also have similar physical explanation if
>> you
>> >take a modal perspective on room dynamics.
>> >
>> >Selon Jay Smalridge <inadaze@mac.com>:
>> >
>> >> Hi all,
>> >> I was wondering if anyone knew if reverberation in a room or a delay in
>> the
>> >> signal creates phase cancellation? I guess the room would have to be
>> small
>> >> to make any significant change, but does the principle still exist?
>> >>
>> >> Thanks
>> >> Jay
>> >>
>> >>
>> >
>> >
>> >%====================================================================%
>> >% Philippe-Aubert Gauthier, B.Ing, M.Sc. %
>> >% Étudiant au doctorat en reproduction de champs acoustiques %
>> >% %
>> >% GAUS (Groupe d'Acoustique et de vibrations de l'Université de %
>> >% [ Sherbrooke) %
>> >% CIRMMT (Centre for Interdisciplinary research in Music, Media %
>> >% [ and Technology) %
>> >% %
>> >% http://www3.sympatico.ca/philippe_aubert_gauthier/acoustics.html %
>> >%====================================================================%
>> >
>> >
>>
>>
>>
>
>
>%====================================================================%
>% Philippe-Aubert Gauthier, B.Ing, M.Sc. %
>% Étudiant au doctorat en reproduction de champs acoustiques %
>% %
>% GAUS (Groupe d'Acoustique et de vibrations de l'Université de %
>% [ Sherbrooke) %
>% CIRMMT (Centre for Interdisciplinary research in Music, Media %
>% [ and Technology) %
>% %
>% http://www3.sympatico.ca/philippe_aubert_gauthier/acoustics.html %
>%====================================================================%
>
>



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