Re: [SoX-users] looking for a really tight (48db) lowpass filter with minimal effect on the remaining stuff

[Rob S. <aq...@ya...>]

> ----- Original Message -----

> 
>> From: Sergei Steshenko <ser...@ya...>
>  
> 
>> --- On Tue, 1/22/13, Rob Sykes <aq...@ya...> wrote:
>>>   Yes, there are several filters available in SoX one could
>>>   try. I don't think a particularly steep filter is needed,
>>>   but also, I don't think you'll hear much difference.
>>  
>> Phase response is audibly irrelevant for pure sine sine inputs.
>>  
>> Pre-echoes is a known phenomena on audio CDs, and the root cause is near 
> brick 
>> wall anti-aliasing filter.
> 
> 
> I was referring to the difference due to the presence or otherwise of content 
> above 16k; i.e. low-pass filtering at 16k is ineffective as a wide-band 
> noise-reduction technique (so there's no point in trying to choose an 
> optimal steepness or phase response for such a filter).
> 
> Cheers,
> Rob


Oops, the OP said 15kHz, not 16kHz, but it makes little difference:

sox -q "|sox -c2 -np synth 3 sin noise remix 1p-2,2p-22" "|sox -c2 -np synth 3 sin noise remix 1p-2,2p-22 sinc -t1k -14500" -d spectrogram