The present invention provides a sinusoidal transform vocoder based on the Bark spectrum, which has high quality and low bit rate for coding. The present invention includes the steps of transforming a harmonic sine wave from a frequency spectrum to a perception-based Bark spectrum. An equal-loudness pre-emphasis and the loudness to a subjective loudness transformation are also involved in the method. Last, a pulse code modulation (PCM) is used to quantize the subjective loudness to obtain quantized subjective loudness. In synthesis, the Bark spectrum is inversely processed to obtain the excitation pattern following the sone-to-phone conversion and equal-loudness deemphasis. Then, the sine wave amplitudes can be estimated from the excitation pattern by assuming that the amplitudes belonging to the same critical band are equal.