import copy


def trim_audio(A, start, stop):
    """Trim copy of MultiSignal audio to start and stop in seconds."""
    B = copy.deepcopy(A)
    assert start < len(B) / B.fs, 'Trim start exceeds signal.'
    for c in range(B.channel_count):
        B.channel[c].signal = B.channel[c].signal[
            int(start * B.fs):
            int(stop * B.fs)]
    return B