Today I entered the PSL to investigate the correlation between sound and PMC, under the direction of Yokozawa-san.
- 10:16 Enter the PSL room, 10:31 Left the PSL room
- I bring the chrome book for portable PEM measurement. In this case, it didn't help me very much for finding noise origin...
- By my ear, I could hear the low frequency sound (in my guess, ~40Hz). I investigated how this sound is occuring and where this sound comes from. I heard the sound strongly from the roof direction, especially pathway at outer room, as shown in Fig.1.
- In the inner room, I couldn't hear that sound strongly. I guess the amplitude of the low-frequency sound (10~100Hz) is hidden by high frequency sound(>100Hz).
- I also checked another side of pathway at outer room. Although I could the sound, it seems to be weaker than another side for me. And I left the room.
After left the PSL room, we investigate the sound origin outside of PSL room.
- We are doubting the precision cooler as sound origin. When previously we checked, we didn't recognized that the bottom of precision cooler makes the low-frequncy sound which I head in PSL room. Probably this sound enters PSL room somehow.
- We took the sound data at several places. The details are listed up in the attached figure.
- From the obtained coherence, the sound around IMC duct didn't affect PMC. So, this duct seems not to be contamination path for sound.
- The coherence between precision cooler and PMC is high. When we compared with coherence between PMC and microphone in PSL room, the coherence in several frequency range are low. I guess the correlated sound is hidden by another loud sound.
- Alghough the coherence measured bottom of door and roof of PSL room were high, we are still not confident about sound contamination path.