A Room Impulse Response Measurement Method Robust Towards Nonlinearities Based on Orthogonal Periodic Sequences

Abstract

An open problem in room impulse response (RIR) measurement is the effect of nonlinearities, especially those with memory, present in the measurement system, specifically in the power amplifier and in the loudspeaker. The nonlinearities can corrupt the measurement introducing artifacts. The paper discusses a RIR measurement method that is robust towards these nonlinearities. The proposed methodology allows measuring the RIR using the cross-correlation method, i.e., computing the cross-correlation between the output signal and an appropriate sequence. In contrast to other cross-correlation based methods, the proposed approach directly estimates the first-order kernel of the Volterra filter modeling the measurement systems, i.e., the system impulse response for small signals. The proposed approach exploits the concepts of orthogonal periodic sequences, recently proposed in the literature. The input signal can be any periodic persistently exciting sequence and can also be a quantized sequence. Measurements performed both on an emulated scenario and in real environments illustrate the validity of the approach and compare it with other competing RIR measurement methods.

Using Periodic Sequences for HRTFs Measurement Robust Towards Nonlinearities in Automotive Audio Applications

“…3. It is clear that all the methodologies present similar results since the car audio system shows a quasi-linear behaviour, following the results we have obtained in [14] for the specific application of room response identification. Other results will be presented in the next section considering a more nonlinear system.…”

“…In this context, we proposed a technique for HRTFs measurement based on perfect and orthogonal periodic sequences that allows an effective measurement robust towards system nonlinearities, as those originated by the power amplifier or the loudspeaker in presence of high reproduction volumes. Starting from the results obtained in [14] and [15], perfect and orthogonal periodic sequences are applied for the first time to the measurement of the HRTFs. Considering a real car environment and an emulated scenario, some results are reported to illustrate the validity of the approach in comparison with other competing HRTFs measurement methods of the state of the art.…”

HRTFs Measurement Based on Periodic Sequences Robust towards Nonlinearities in Automotive Audio

“…Together with the already-mentioned nonlinear distortions introduced by the electro-acoustic system, the measurement is influenced by the characteristics of the sound sources, especially in near-field measurements [ 2 ], and environmental disorders, such as external noise, sound reflections, and temperature changes [ 31 ]. The use of a controlled environment, such as an anechoic chamber, can avoid some of these problems, e.g., noise, reflections, and temperature changes, while the nonlinear distortions can be prevented by choosing an effective measurement method and stimuli [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].…”

“…Later, Ref. [ 40 ] introduced the OPSs, which were applied to the robust room impulse response measurement in [ 37 , 39 ]. The OPSs allow the identification of a broad class of nonlinear filters, the functional link polynomial (FLiP) filters.…”

Robust selection of clean swept-sine measurements in non-stationary noise

“…Similarly, cross correlation was used as a measure to estimate IRs sensitivity to small changes in sound-source position 35 as well as for robust IR measurement against nonlinearities. [36][37][38] This suggests that parameters related to similarity are good indicators of changes in audio signals, even when the environment is not free from noise.…”