Re: Test report MBP built-in audio device
Re: Test report MBP built-in audio device
- Subject: Re: Test report MBP built-in audio device
- From: "Mikael Hakman" <email@hidden>
- Date: Wed, 27 Aug 2008 01:14:40 +0200
- Organization: Datakonsulten AB
Being scientist myself, and having mathematical, physical chemistry and
computer sciences university degrees I would appreciate very much to hear
your opinion. Let me first explain how my experiments are conducted so that
we both understand expression "start-up time" in the same way.
I'm not physically, electronically or even logically switching the device
on. The device is on for a long period of time and it is feed by a
continuous signal. The signal consists of silence (zeros) up to a certain
time. At that time the signal becomes pure sine wave with phase 0 (i.e.
first sine sample is sin(0), next is sin(dt) etc). I continuously record
output from the device and I know the exact delay between my output into
device and device's output into my program. Therefore I know which of
recorded samples that corresponds to the first sine wave sample. I start my
analysis from that sample. When I say that I know the exact delay I mean the
exact number of samples, which of course vary a little between the runs but
is measured at the very beginning of each run, earlier (before silence and
sine wave) in the test signal so to speak.
The reason I'm using such a test signal is that it is a crude simulation of
what happens when a musical instrument is played. Because proper
reproduction of signal during instrument's attack time (first few
milliseconds after you hit a string, start blowing etc) has been shown to be
the second most important factor after harmonic content to our perception of
timbre, I decided to measure distortion in experiments that are close to
this musical reality. Perhaps such experiments could explain why 2 audio
devices having the same or very close specs, may sound so differently, one
sounds right, the other doesn't.
I would appreciate very much your view on the subject.
Best Regards,
Dr. Mikael Hakman
Uppsala, Sweden
On Tuesday, August 26, 2008 11:52 PM, Brian Davies wrote:
I suggest that some combatants in this war rest their itchy typing fingers
until they properly understand the subject matter.
Brian Davies
Mathematical Sciences Institute
Australian National University
email@hidden
www.maths.anu.edu.au/~briand
PS: all signal processing, including valve and other electronic
equipment, has a start-up time which is irrelevant to distortion or
otherwise of transitory audio material.
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