Laboratory Setup
Room and Equipment
The earplug evaluations use the same custom acoustic testing laboratory as our hearing device evaluations, with slightly different measured room properties due to ongoing improvements.
The walls and ceiling are filled with sound-absorbing material between studs (e.g., RockWool Safe 'n Sound Insulation) and the floor is carpeted.
| Parameter | Value |
|---|---|
| Ambient sound pressure level | 34 dB LAeq (A-weighted) |
| 4-frequency average RT60 (0.5, 1, 2, 4 kHz) | 0.059 s |
| Estimated critical distance | 1.5 m |
We installed a ring of 8 speakers (Yamaha HS5) with a radius of 1 m -- ensuring that at the center of the ring the direct sound from the speakers dominates any room reverberation. Each speaker is equalized to be flat ( 2 dB) from 50 to 15,000 Hz.
Figure 1. Test lab floorplan (3.96 m x 3.96 m room with 8-speaker ring)
We placed an acoustic manikin (KEMAR 45BA) in the center of the speaker ring. The height of its artificial pinnae was aligned with the high-frequency drivers (tweeter) of the speakers. The manikin has:
- Anthropometric pinnae (KB5000/KB5001)
- Standard IEC 60318-4[4] ear simulators (GRAS RA0401)
- A wig
- Internal cavities filled with sand
The microphone outputs are digitized by a high quality audio interface (Antelope Orion Studio).