def change_speed(body, speed=1):
    """Change the voice speed of the wave body."""
    if speed == 1:
        return body
    length = int(len(body) * speed)
    rv = bytearray(length)
    step = 0
    for v in body:
        i = int(step)
        while i < int(step + speed) and i < length:
            rv[i] = v
            i += 1
        step += speed
    return rv
