Sound calibration
Introduction
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Sensitivity of speakers
- In all our labs we use the Cambridge Audio MINX MIN12 speaker.
- The speaker has a specified sensitivity of 86 dB SPL (@2.83 Vrms input)
- The calibration is calculated @ 1Vrms input and depends one over the square of the distance of the speaker to the center of the subjects head.
Calibration = mag2db(db2mag(Sens@1V)/Distance^2)
Table: calibration (@ 1Vrms and 1kHz) in different labs.
| LAB | Distance (m) | Calibration(dB SPL) | Measured (dB SPL) |
|---|---|---|---|
| TEST LAB | 1.00 | 80 | ? |
| AUDITORY PERCEPTION LAB | 1.05 | 76.1 | ? |
| AUDITORY SPHERE LAB | ? | ? | ? |
| AUDITORY MOTION LAB | ? | ? | ? |
| NIRS EEG LAB | ? | ? | ? |
Sensitivity of headsets
A commercial headset normally have a higher impedance than an audiological headset and therefore a higher sensitivity.
Table: impedances and sensitivity @ 1mW and @ 1V for Headphones measured @ 1 kHz
| Model | Impedance (Ohm) | Sens@1mW (dB SPL) | Sens@1V (dB SPL) | Difference (dB) | Audiological |
|---|---|---|---|---|---|
| AKG_K271_MKII | 55 | 91 | 104 | 12.5 | N |
| SENNHEISER_HD600 | 300 | (92) | 97 | 5.2 | N |
| SENNHEISER_HD100 | 26 | (94) | 110 | 15.8 | N |
| BEYERDYNAMIC_DT_770_PRO | 80 | 96 | (107) | 11.0 | N |
| SENNHEISER_HDA280 | 37 | (103) | 117 | 14.3 | Y |
| SENNHEISER_HDA300 | 23 | (108) | 124 | 16.4 | Y |
| RADIOEAR_P4492 | 10 | (107) | 127 | 20 | Y |
| TELEPHONICS_TDH-39P | 10 | (108) | 128 | 20 | Y |
- The numbers are from the specs on the internet.
- The numbers between brackets are calculated from the difference between the 1mW and 1V sensitivity by: Sens(1V) = Sens(1mW) + 10*log10(R/1000)