[Yokozawa, Yuzurihara]
We measured the instrumental noise of three microphones (two mic of B&K and one mic of aco). Related k-log : Investigation of self-noise of microphone (B&K 4188-A-021)
We use three channel correlation method to evaluate the instrumental noise, which was used in evaluating seismometer by Miyo-san (2016) and Sekiguchi-san (2013).
Set-up
We used PEM IY0 rack. The microphones are installed at the 1m hight. See the attached figure.
Channel names are
- K1:PEM-SENSOR_RACK_IY0_DSUB25_OUT_DQ (B&K 4188-A-021, S1808976) (gain=1000)
- K1:PEM-SENSOR_RACK_IY0_DSUB26_OUT_DQ (B&K 4188-A-021, S1808974) (gain=1000)
- K1:PEM-SENSOR_RACK_IY0_DSUB27_OUT_DQ (ACO 4152N, S2011970) (gain=100)
Measurement log
2021/04/23 Fri
10:22 Finished the set-up
10:29 ~ 10:36 [measurement 1]
- No injection, just background noise
- The measurement environment was not quiet. Later we need to find the quiet data segment.
10:44 ~ 10:50 [measurement 2]
- We injected the white acoustic noise of 20Hz ~ 1860Hz by the speaker.
- 20Hz is the lower limit of the microphone's sensitive bandwidth.
- There is no special reason for the upper limit. The sampling rate for this channel is 1 kHz, so injection above 512 Hz is meaningless.
- The speaker is placed so that the sound radiation surface is perpendicular to the ground.
10:57 ~ 11:03 [measurement 3]
- Except for the direction of speaker, the set-up is same as [measurement 2].
- The speaker is placed so that the sound radiation surface is parallel to the ground.
11:15 ~ 11:20 [measurement 4]
- Except for the direction of speaker, the set-up is same as [measurement 2].
- The speakers are placed so that the sound radiation surface is perpendicular to the ground and at the same height as the microphone.
For the detailed memo, please check pdf.
The calibration and actual evaluation of instrumental noise will be done soon.
