[78-L] Reversing audio (was: 78-L Digest, Vol 22, Issue 17, was Why I Hate LPs)

Doug Pomeroy audiofixer at verizon.net
Mon Jul 12 06:57:12 PDT 2010

I assume Mike is referring to Mark Hood's talk?
I missed it (will watch when it is finally posted on the ARSC web site),
but I spoke to Mark about his talk (and his examination of waveforms
produced by playing analog tapes in reverse) but he didn't mention
anything about digitally reversing audio, and I cannot imagine why
reversing the order of digital samples would have any deleterious
effects. Bits is bits, no?

Doug Pomeroy
audiofixer at verizon.net

> Message: 11
> Date: Sun, 11 Jul 2010 18:23:23 -0400
> From: Michael Biel <mbiel at mbiel.com>
> Subject: [78-L] Reversing audio (was: 78-L Digest, Vol 22, Issue 17,
> 	was Why I Hate LPs)
> To: 78-L Mail List <78-l at klickitat.78online.com>
> Message-ID: <4C3A445B.4050302 at mbiel.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Rob Spencer wrote:
>> On 7/11/2010 12:00 PM, Steve Barr wrote:
>>> A microgroove LP can often develop skips/sticks that arise from
>>> (presumably) groove damage...which is (1) invisible to the naked
>>> human eye...and (2) impossible to correct?!
>> I had a skip of this type to deal with recently when dubbing a  
>> record.
>> Happily, my phonograph has a reverse gear, and in reverse the record
>> didn't skip. I then reversed the resultant file in my sound editor.
>> Rob Spencer
> We had a session at ARSC in New Orleans which demonstrated that
> reversing recordings digitally must NOT be done.  They demonstrated  
> how
> a square wave turns into curicules and regular sound waves become  
> almost
> unrecognizable in comparison to the original.  They might sound ok but
> they aren't.   Sound can be reversed in analogue with minimal  
> problems,
> but even there you can run into an absolute-phase issue if you are not
> careful. But NEVER EVER reverse audio in the digital domain.
> Mike Biel   mbiel at mbiel.com

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