Improvement of the measurement quality of loudspeaker characteristics under reverberant/noisy conditions

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K11872
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 61010:Perceptual information processing-related
• Research Institution: Tokyo Denki University
• Principal Investigator: Kaneda Yutaka 東京電機大学, 工学部, 研究員 (20328511)
• Co-Investigator(Kenkyū-buntansha): 池田 雄介 東京電機大学, 未来科学部, 教授 (80466333)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: スピーカ特性 / インパルス応答 / 反射音低減 / 群遅延 / 逆フィルタ / 無響室 / 等価音源モデル / 虚像法

Outline of Final Research Achievements

Low-frequency reflective sounds degrade the measurement results of the impulse response of a loudspeaker in a small-scale anechoic room. A basic countermeasure entails cutting out the direct sound before the arrival time of the reflective sounds. However, since the response of a loudspeaker is delayed in the low frequency range, part of the response in the low frequency range is truncated, resulting in measurement errors. In this research, we propose a method of obtaining the group delay of a loudspeaker from near-field measurements, correcting the delay in the low-frequency range by using an inverse filter, and extracting the direct sound. We confirm that the proposed method can greatly reduce the effect of reflective sounds. Moreover, we propose a measurement method with noise reduction and improve the estimation method for early impulse responses around a microphone array from a small number of measurements to investigate its potential application to sound field control.

Free Research Field

音響信号処理

Academic Significance and Societal Importance of the Research Achievements

音響インパルス応答は、さまざまな音響特性量が導出できる基本特性量であるため、その高品質な計測は大変重要である。しかし、音場には雑音や反射音が存在し、品質劣化要因となる。本研究で提案した反射音、雑音の軽減方法は、無響室に限らず一般室にも拡張可能と考えられ、これらの問題に対する改善策を与えたものと考える。また、音場制御等において多数のインパルス応答が必要となるが、本研究が提案した推定方法は効果的と考える。