Toward a cylinder pressure signals-based active synthesis algorithm for engine sound

Abstract

The active sound design (ASD) technology is one of the most flexible methods to achieve the diverse design of automobile sound, in which the active sound synthesis algorithm is essential. However, in previous works, the discontinuity phenomena always appear in the synthesized sound. Thus, a new method of active engine sound synthesis based on cylinder pressure signals is proposed in this paper for the sound synthesis algorithm of ASD technique. Firstly, the index matrix of sound grains is constructed based on the periodicity of engine cylinder pressure signal. Then the frame length and frame shift are defined by tracing the time step of Revolutions Per Minute (RPM) of engine, and the hamming window function is constructed to extract sound grains. Subsequently, the overlap-and-add (OLA) method is used to realize the synthesis of engine sounds with different durations. In addition, the code program of proposed algorithm is written and the ASD prototype system is built respectively to synthesize the engine sounds. Finally, a similarity evaluation metric is defined to verify the effectiveness of proposed algorithm. The results show that our algorithm not only restitutes the main features of original sound, but also satisfies both the real-time feedback on the driving status and the continuity of synthesized sound. It contributes to the development of real-time ASD engineering for automobiles.