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The interface is object-oriented, and provides the methods below.

=over 4

=item $audio = Audio::Data->new([method => value ...])

The "constructor" - takes a list of method/value pairs and calls
$audio->I<method>(I<value>) on the object in order. Typically first "method"
will be B<rate> to set sampling rate of the object.

=item $rate = $audio->rate

Get sampling rate of object.

=item $audio->rate($newrate)

Set sampling rate of the object. If object contains existing data it is
re-sampled to the new rate. (Code to do this was derived from a now dated
version of C<sox>.)

=item $audio->comment($string)

Sets simple string comment associated with data.

=item $string = $audio->comment

Get the comment

=item $time = $audio->duration

Return duration of object (in seconds).

=item $time = $audio->samples

Return number of samples in the object.

=item @data = $audio->data

Return data as list of values - not recommended for large data.

=item $audio->data(@data)

Sets elements from @data.

=item $audio->length($N)

Set number of samples to I<$N> - tuncating or padding with zeros (silence).

=item ($max,$min) = $audio->bounds([$start_time[,$end_time]])

Returns a list of two values representing the limits of the values
between the two times if $end_time isn't specified it defaults to
the duration of the object, and if start time isn't specified it defaults
to zero.

=item $copy = $audio->clone

Creates copy of data carrying over sample rate and complex-ness of data.

=item $slice = $audio->timerange($start_time,$end_time);

Returns a time-slice between specified times.

=item $audio->Load($fh)

Reads Sun/NeXT .au data from the perl file handle (which should
have C<binmode()> applied to it.)

This will eventually change - to allow it to load other formats
and perhaps to return list of Audio::Data objects to represnt
multiple channels (e.g. stereo).

=item $audio->Save($fh[,$comment])

Write a Sun/NeXT .au file to perl file handle. I<$comment> if specified
is used as the comment.

=item $audio->tone($freq,$dur,$amp);

Append a sinusoidal tone of specified freqency (in Hz) and duration (in seconds),
and peak amplitude $amp.

=item $audio->silence($dur);

Append a period of 0 value of specified duration.

=item $audio->noise($dur,$amp);

Append burst of (white) noise of specified duration and peak amplitude.

=item $window = $audio->hamming($SIZE,$start_sample[,$k])

Returns a "raised cosine window" sample of I<$SIZE> samples starting at specified
sample. If I<$k> is specified it overrides the default value of 0.46
(e.g. a value of 0.5 would give a Hanning window as opposed to a Hamming window.)

  windowed = ((1.0-k)+k*cos(x*PI))

=item $freq = $audio->fft($SIZE)

=item $time = $freq->ifft($SIZE);

Perform a Fast Fourier Transform (or its inverse).
(Note that in general result of these methods have complex numbers
as the elements. I<$SIZE> should be a power-of-two (if it isn't next larger
power of two is used). Data is padded with zeros as necessary to get to
I<$SIZE> samples.

=item @values = $audio->amplitude([$N[,$count]])

Return values of amplitude for sample $N..$N+$count inclusive.
if I<$N> is not specified it defaults to zero.
If I<$count> is not specified it defaults to 1 for scalar context
and rest-of-data in array context.

=item @values = $audio->dB([$N[,$count]])

Return amplitude - in deci-Bells.
(0dB is 1/2**15 i.e. least detectable value to 16-bit device.)
Defaults as for amplitude.