Noise Reduction Performance of Various Signals for Impulse Response Measurement

In the measurement of impulse response, ambient noise is included leading to a decrease in measurement quality. To solve this problem the use of several measurement signals (or excitation signals) has been proposed. However, the relationship between measurement signals and the noise reduction performance (NRP) has not been quantitatively examined thus far. In this study the NRP characteristics of different measurement signals were theoretically examined to derive equations that can determine NRP from the spectra of the measurement signal and noise. From the theoretical and experimental examinations the following results were obtained. The NRP for white signals and noise-whitening signals is actually the same. Only the minimum noise (MN) signal that minimizes the noise component showed a significant improvement in NRP. A pink spectrum measurement signal showed good NRP in the presence of 1/k(2) spectrum noise, where k is the discrete frequency number, but worse performance with other types of noise. This supports the conclusion that using the MN signal, which has a power spectrum that is the square root of the power spectrum of the noise, is the best method of reducing the effect of noise on the measured impulse response.