In article , John Phillips
wrote:
On 2006-03-18, Don Pearce wrote:

No, no ambiguity, dB below full scale does not depend on wave shape,
merely how many digital levels remain unused.

This puzzled me.

The first quote (from don, not Don) is the opening part of the DBFS
entry in Wikipedia - see http://en.wikipedia.org/wiki/DBFS. I think it
is correct at least up to the final sentence about ambiguity. Then it
becomes at least ambiguous itself.

The actual ambiguity seem to be whether, when a waveform is said to have
amplitude x dBFS, you mean the peak amplitude of the waveform or its RMS
amplitude. Thus I think the fundamental ambiguity is not as stated in
the Wikipedia article about whether you use a sine or square wave as
reference.

Like Don (not don) I always assumed with dBFS you implicitly meant the
peak value of the waveform because of the nature of its representation
in a system having a waveform-independent overload level of 0 dBFS.

Alas, this is another one of the areas where it is easy for statements to
be ambiguous. Partly due to the confusions between instantaneous peak
levels versus rms, partly due to unspoken assumptions at times that you are
dealing with a sinewave.

To make things even more confusing wrt terminology I am currently doing
measurements and statistics of how the 'short term' peak level varies with
time with some audio waveforms. Thus I'm using peak levels, and then having
to say what the 'peak' peak level is, and how often a given 'peak' level
occurs... There are times when normal English can become hard to use to
deal with such things. :-)

Slainte,

Jim

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