Reverberation Time

The reverberant sound in an auditorium dies away with time as the sound energy is absorbed by multiple interactions with the surfaces of the room. In a more reflective room, it will take longer for the sound to die away and the room is said to be 'live'. In a very absorbent room, the sound will die away quickly and the room will be described as acoustically 'dead'. But the time for reverberation to completely die away will depend upon how loud the sound was to begin with, and will also depend upon the acuity of the hearing of the observer. In order to provide a reproducible parameter, a standard reverberation time has been defined as the time for the sound to die away to a level 60 decibels below its original level. The reverberation time can be modeled to permit an approximate calculation. .

Rationale for 60dB Reverberation Time

The reverberation time is perceived as the time for the sound to die away after the sound source ceases, but that of course depends upon the intensity of the sound. To have a reproducible parameter to characterize an auditorium which is independent of the intensity of the test sound, it is necessary to define a standard reverberation time in terms of the drop in intensity from the original level, i.e., to define it in terms of relative intensity.

The choice of the relative intensity to use is of course arbitrary, but there is a good rationale for using 60 dB since the loudest crescendo for most orchestral music is about 100 dB and a typical room background level for a good music-making area is about 40 dB. Thus the standard reverberation time is seen to be about the time for the loudest crescendo of the orchestra to die away to the level of the room background. The 60 dB range is about the range of dynamic levels for orchestral music. 选择使用的相对强度当然是任意的，但使用60分贝是有充分理由的，因为大多数管弦乐的最响亮的高潮大约是100分贝，而一个良好的音乐演奏区域的典型背景水平大约是40分贝。因此，标准的混响时间被看作是管弦乐最响亮的高潮衰减到房间背景水平所需的时间。60分贝的范围大约是管弦乐音乐的动态水平范围。

What is a desirable reverberation time?

The optimum reverberation time for an auditorium or room of course depends upon its intended use. Around 2 seconds is desirable for a medium-sized, general purpose auditorium that is to be used for both speech and music. A classroom should be much shorter, less than a second. And a recording studio should minimize reverberation time in most cases for clarity of recording.

The reverberation time is strongly influenced by the absorption coefficients of the surfaces as suggested in the illustration, but it also depends upon the volume of the room as shown in the Sabine formula. You won't get a long reverberation time with a small room.

Reverberation Time Calculation

Approximate reverberation times can be calculated from the Sabine formula:

Modeling a room of Height H =m = ft 高度 H = m = ft 中文译文中的待填/计算数值依次对应：1：h 2：hc。实际数值以上方原输入框为准。 Length L =m = ft 长度 L = m = ft 中文译文中的待填/计算数值依次对应：1：l 2：lc。实际数值以上方原输入框为准。 Width W =m = ft 宽度 W = m = ft 中文译文中的待填/计算数值依次对应：1：w 2：wc。实际数值以上方原输入框为准。 with absorption coefficients: 吸收系数： 建模一个房间的

awalls=, a walls = ,（专名或术语） 中文译文中的待填/计算数值依次对应：1：aw。实际数值以上方原输入框为准。

afloor 地板

=,

aceiling 天花板

= for average of 等于平均 中文译文中的待填/计算数值依次对应：1：ac。实际数值以上方原输入框为准。

aavg 平均加速度

=

gives an effective absorbing area of Se 提供有效的吸收面积 S e

=m2 = ft2 = m² = ft² 中文译文中的待填/计算数值依次对应：1：se 2：sec。实际数值以上方原输入框为准。

for a room of volume V =m3 = ft3. 对于体积为 V = m³ = ft³ 的房间。 中文译文中的待填/计算数值依次对应：1：v 2：vc。实际数值以上方原输入框为准。

The corresponding reverberation time is 相应的混响时间是

RT60 RT60

=seconds. 等于秒。 中文译文中的待填/计算数值依次对应：1：rt。实际数值以上方原输入框为准。

Examples of Reverberation Times

One way to respond to the question "What is a good range of reverberation times for concert halls?" is to give examples of some of the most famous halls in the world. For the overall average reverberation times:

But the overall average reverberation time does not tell the whole story. The variation of reverberation time with frequency is also important.: