Measuring variation of loudness in consideration of arrival direction and distribution width of sound

In this study, we examine the changes in loudness due to the arrival direction and distribution width of a sound. Loudness is conventionally measured by using an omnidirectional microphone. However, this measurement does not take into account the influence of diffraction caused by a listener's head and auricles. That is, it does not include any information on the arrival direction and distribution width of a sound. Loudness was measured by taking the direction and width into account with a dummy head, and subjective tests were conducted to compare the test results with those measured by using the head. It is revealed that loudness varies depending on the arrival direction and distribution width of a sound source, and it differs from that measured by using an omnidirectional microphone. Additionally, it is possible to quantitatively determine the variation in loudness (as a sound pressure level) from the arrival direction and distribution width of a sound source for noise evaluation.