Search Results

This paper describes an objective evaluation method for the engine sound quality in a car interior during acceleration. Two principal factors, pleasantness and raciness, of the engine sound quality were found with a subjective evaluation test in a laboratory. Psycho-acoustic indexes corresponding to these factors were revealed by investigating the correlation among subjective ratings and acoustic characteristics. The index of raciness was originally proposed for the assessment of sound that makes driving fun when the sound is emphasized. We propose that the design of engine sound is required with consideration of the balance between pleasantness and raciness.

This paper presents a new method of synthesizing exhaust noises for modulating their timbre based on the order components of engine revolution. This method makes it possible to synthesize exhaust noises in real-time using a computer system with an ordinary digital signal processor, because this method uses inverse Fourier transform in its main processing part to make waveforms from order components of engine revolution. For example, the speed of calculation by this method is about 100 times higher than that by an ordinary direct method in the case of a variable acceleration curve. Since this method guarantees the continuity of the waveform between processing segments, a good sound quality ca be provided for various modulations of noise timbre.

A new portable ride comfort meter was developed, which gives a new index called “VN” (Vibration Number) as an objective measure of ride comfort of passenger cars. In order to develop this apparatus, the subjective evaluation test on whole-body vibration was carried out using the dual axis vibration table. This ride comfort meter is composed of a calculator for converting measured vibration inputs to a human body into “VN”, three accelerometers connected to the calculator and weighting filters for adjusting an accelerometer output to vibration feeling. One accelerometer detects a vertical vibration input at seat cushion, another detects a vertical vibration input at feet and the other detects a lateral vibration input at seat back. The VN index indicated by the apparatus is fixed at zero corresponding to the threshold of seated person to vertical vibration in case when no vibration exists at feet and seat back, and fixed at one hundred corresponding to the short time exposure limit.