[Bradford] Convert wave amplitude into a float

[david at nucleon.co.uk]

Does seem a bit like they are trying to reinvent the wheel.

There is already off-the-shelf hand-held kit available that does FFT
spectrum analysis. We use it all the time, where I work.

There is also condition monitoring software that "learns" the
characteristic noise spectrum of equipment, and flags up anomalies (20
years ago I even had a next-door-neighbour who's PhD was in the subject).

Some relevant kit is sold here:
http://www.bksv.com/Products/analysis-software/acoustics/noise-source-identification

Dave B

> I think Dave (S) is right,
>
> I guess they are going to be doing frequency-amplitude analysis, which is
> commonly done by Fast Furiour Transforming samples into groups of
> frequency-amplitude (think graphic equaliser). FFT is much easier to
> program with floating point samples.
>
>
> On 20 March 2014 20:49, John R. Hudson <j.r.hudson at virginmedia.com> wrote:
>
>> Thanks for all the suggestions which I will pass on if they haven't
>> joined the mailing list yet. Because they want to do it continuously,
>> reading the Alsa PCM device seems the most likely route. But maybe one
>> of the other options will be more useful for them once they investigate
>> them.
>>
>> However, thanks for the suggestion about how to export from Audacity as
>> that will enable them to use the data they have already collected to
>> develop the software before they need to apply to an actual stream.
>>
>> John
>> --
>> On Thu, 2014-03-20 at 20:25 +0000, David Spencer wrote:
>> > What they *really* want to do is probably some kind of realtime signal
>> > processing... which is not what Audacity is for (it's an editor).
>> > They should probably be looking at reading the Alsa pcm device
>> > directly (e.g. from Python); I bet that's what is pencilled in to
>> > consume these hypothetical floats... either that, or the hypothetical
>> > float-consumer needs to read an arbitrary well-understood audio file
>> > container (e.g. WAV) using a library routine. Once the ints are in a
>> > program, It's not rocket science to convert ints to floats prior to
>> > feeding them to whatever other library routines are processing the
>> > data (fft or whatever).
>> >
>> > The audacity question as posed just sounds like they caught the first
>> > bus that came along :-)
>> >
>> > -D.
>> >
>> >
>> > On 20 March 2014 17:46, John R. Hudson <j.r.hudson at virginmedia.com>
>> wrote:
>> > > Hi
>> > >
>> > > I popped in to see Paul Cannon this afternoon and they had just hit
>> a
>> > > problem - how to convert a wave amplitude as displayed in Audacity
>> into
>> > > a float which can be fed into another program.
>> > >
>> > > There is no obvious way in which to do this from Audacity. So it may
>> > > involve using different software.
>> > >
>> > > Any thoughts very welcome.
>> > >
>> > > John
>> > > --
>> > >
>> > >
>> > >
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>>
>>
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