音乐厅音质设计中响度评价参量的讨论

A review of sound strength criterion in acoustical design of concert halls

强感级(G,dB)是评价音乐厅音质设计中重要客观参量之一,它由厅内声级按标准声源的声功率级归一化得出。我们不仅考察厅内的总强感级G,还得分别考虑其早期声和后期声的G_早和G_后,因为它们的成因和主观效果是不同的。近年从主观试验结果中获得一个意外发现,即最低频段的G低值与中频G_中值之比,将是决定厅内低音感的主要因素,而不是过去所说的低频和中频混响时间之比。10年前,人们认为环绕感LEV只由到达听者耳际的侧向声能所决定,如今则了解到后期总声能G_后这一因素也很重要。并提出由G和侧向比值LF来估算LEV的新公式,便于设计考虑。本文对音乐厅最佳G值作了讨论。近年的一个重要发现是,音乐厅内听者响度判断主要由混响声决定,或认为因视听综合心理效应使听者的响度判断与离舞台距离几乎无关,或两者兼具。后者涉及视觉信息输入影响听觉响度体验,即所谓多维感知综合效果的心理学问题。近年有人认为G参量不能直接反映音乐厅内听众听到的绝对声压级为由,提出以音乐片段中乐队齐奏强音标志段声级L_(pf)作为评价音乐厅响度的新物理指标。作者对此作了全面评析,说明其存在问题和不可行性。

An important objective parameter in the acoustical design of concert halls is the sound strength G（dB）.This parameter G is denoted as the sound level in an auditorium normalized to the sound power level of the source.Besides the total level of G in the auditorium,the early（80 ms） and late sound field,G_E and G_L should also be considered separately because the causing factors and subjective effects of these fields are so different.A surprising result from a series subjective experiments showed that the bass perception in a concert hall is highly related to the strength factor at lowest frequencies,not the reverberation time factor as formerly considered.It was commonly recognized before that the most important component of listener envelopment（LEV） is the late energy arriving at a person＇s ears from lateral directions only.Now we know the strength factor G should be included,and the total late energy G_（late） is a better component of LEV than late lateral energy.Some LEV predicted formula has been devised accordingly for acoustical design purpose.Criterion for acceptable loudness is reviewed in this paper.An important new discovery on this subject shows that listeners＇ judgment of loudness in a hall is based on the strength of the reverberant field or on the vision of the distance of the source—-probably on both.Some uncertainties remain regarding objective correlates of ＇intimacy＇. The mean forte sound pressure level of tutti-sound,a so called new criterion parameter was recommended by Wu to describe the subjective loudness perception in concert halls during the performance.The author gives criticism on this recommendation and also points out neither the measurement procedure nor evaluation method is feasible.