Downsampling an object of class Wave or class WaveMC.
downsample(object, samp.rate)Sampling rate the object is to be downsampled to.
samp.rate must be in [2000, 192000];
typical values are 11025, 22050, and 44100 for CD quality.
If the object's sampling rate is already equal or smaller than samp.rate,
the object will be returned unchanged.