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Sound Quality is one of the most important factors to achieve a successful design for Engine Air Induction Systems. Vehicle and bench testing, and simulation tools can be used in order to optimize and refine emitted noise. One difficulty on using simulation in advanced development phases is the necessity to interpret the response curves and assess if sound quality is acceptable. One recent and promising area to help simulation interpretation is the sound synthesis of the emitted noise. This paper presents a simple procedure and example with the objective of reproducing the emitted noise, which allows subjective assessments of different tuning concepts. The example, even a simple one, shows the advantage to finally hear what was simulated.

The constant Q transform consists of a geometrically spaced filter bank, which is close to the wavelet transform due to the feature of its increasing time resolution for high frequencies. On the other hand, it can be processed using the well-known FFT algorithm. In this sense, this tool is a middle term between Fourier and wavelet analyses, which can be used for stationary and non-stationary signals. Automotive NVH signals can be stationary (e.g., idle, cruise) or non-stationary, i.e., time-varying signals (e.g., door closing/opening, run-up, rundown). The objective of this work is to propose the use of the constant Q transform, developed originally for musical signal processing, for automotive NVH (run up, impact strip and door closing) time-frequency analyses. Also, similarities and differences of the proposed tool when compared with Fourier and wavelet analyses are addressed.