transforms.go
func FullWaveRectifier(buf *audio.FloatBuffer) error {
	if buf == nil {
		return audio.ErrInvalidBuffer
	}
	for i := 0; i < len(buf.Data); i++ {
		buf.Data[i] = math.Abs(buf.Data[i])
	}

	return nil
}
func FullWaveRectifier(buf *audio.FloatBuffer) error {
	if buf == nil {
		return audio.ErrInvalidBuffer
	}
	for i := 0; i < len(buf.Data); i++ {
		buf.Data[i] = math.Abs(buf.Data[i])
	}

	return nil
}
// FullWaveRectifier to make all signal positive
// See https://en.wikipedia.org/wiki/Rectifier#Full-wave_rectification