关于双混响室测隔声材料?

minoz

用两个相邻混响室测隔声材料，隔墙开窗（以便放待测材料），由一个混响室内的声源发声，测两个混响室中的声压差。但是发现第一间声场中沿声源到隔墙窗方向有随距离2dB的衰减，不是完全混响，这是为什么呢？在测量中需要注意些什么呢

zhangzy

混响室测隔声是基于两个房间都是扩散场的假设。扩散场意味着各点能量密度相同，不相干声波来自所有方向。混响室的低吸声和不规则墙体使它接近扩散场，但不可能成为理想扩散场，至少在靠近声源（来自声源的直达声太强）或墙（反射波干涉）的地方。
题主的问题可能是由于声源离测试材料太近或者麦克风离声源太近造成的。麦克风需要多选几个位置， ISO 140里有推荐一些声源和麦克风的设置，我复制粘贴几段：

• Place the loudspeaker enclosure so as to give a sound field as diffuse as possible and at such a distance from the separating element and the flanking elements influencing the sound transmission that the direct radiation upon them is not dominant.
• Microphone positions：The following are minimum separating distances:
  
  • 0,7 m between microphone positions;
  • 0,5 m between any microphone position and room boundaries or diffusers;
  • 1,0 m between any microphone position and the sound source.
  • NOTE Greater separating distances should be used wherever possible.
    
• Ensure that the microphone positions are outside the direct sound field of the source. Each fixed microphone position shall lie outside the region in which levels decrease significantly with distance from the source.
• Guidance on the selection of optimum source positions
  
  • The suitability of source positions also depends on the radiation characteristic of the loudspeaker as well as on the microphone positions (or the microphone path in the case of a moving microphone).
  • The distance between different loudspeaker positions shall be not less than 0,7 m.
  • At least two positions shall be not less than 1,4 m apart.
  • The distance between the room boundaries and the source center shall be not less than 0,5 m.
  • Different loudspeaker positions shall not be located within the same planes parallel to the room boundaries.
  • Deviating from the above-mentioned requirements concerning the distance between the room boundaries and the source, especially in small rooms it is often of advantage for the practical execution of the measurements to use loudspeaker positions in the corners of the source room. Take special care with regard to possible influence on the flanking transmission and with regard to unwanted increase of level fluctuations in the source room.
    

think2015

你的声源室声源没有完全混响这个应该是合理的，因为声源发出噪声有直达声和反射声，直达声是由设备发出向外扩散的声源，混响是经过反射的了，直达声是有距离衰减规律的，在声源太近的位置没有达到混响，直达声占主流，这个应该是正常的，ISO140或者GB/T19889规定了你在声源室布置测点要离开声源一定距离的，你只要在这个控制的范围外取点，应该是可以的，至于你说的衰减问题，你评价是否可行的办法是标准里，GB/T19889.1等对于声压级声场均匀度的标准来去考核，因为你提到的这个我不清楚你具体布点，如果你有个点离声源太近，那出现这个现象是正常的，你不应该取声源过近的点

Apologize

两个混响室测隔声？你们用的哪个标准？我们从来都是声源混响 Mic放消声室啊