G.R.A.S. SOUND & VIBRATION
Page 14
Hearing-Protector Test Fixture Type 45CA
4.4
Acoustic Isolation Testing
ISO 4869-3 section 5.1.4 specifies a minimum acoustic isolation for the test fixture.
Cup GR0974 and Plug GR1079 (Fig. 2.1) are provided to check this.
1.
Start with Type 45CA fitted with a microphone as described in the previous section.
2.
Remove the Insert GR0970 surrounding the microphone (Fig. 4.12).
3.
Push the Cup GR0974 with its hollow facing the microphone into the recess surrounding the
microphone until it makes contact with the base of the recess (Fig. 4.13).
4.
Fig. 4.14: On the
opposite
side of the Type 45CA, push Plug GR1079 into the hole as far
as it will go. For sound leakage sealing, apply Silicon Grease MI0016 to the plug.
5.
Type 45CA is now ready to be tested for acoustic isolation (Fig. 4.15).
Fig. 4.12
Fig. 4.13
Fig. 4.14
Fig. 4.15
Acoustic Cup
GR0974
Vacate
recess
Insert
GR0970
1.5 mm
screw
Push until
cup makes
contact
with base
of recess
Inner edge
Acoustic
Plug
GR1079
Acoustic
Cup
GR1079
Push plug until
its inner edge
makes contact
with base of
recess
Plug
GR1079
