G.R.A.S. SOUND & VIBRATION
G.R.A.S. SOUND & VIBRATION
4
45CA Headphone/Hearing-Protector Test Fixture
1 Introduction
1.1
About this Appendix
The 45AC comes fully assembled from the factory. However, for maintenance purposes, details
about how it is assembled are needed. Therefore, this appendix explains how the 45CA test
fixture and its various configrations are assembled.
The appendix consists of the following parts:
Section 1 gives a brief overview of the basic test fixture.
Section 2 lists the parts used for the basic test fixture.
Section 3 describes how it is assembled.
Section 4, 5 and 6 explains how the application specific configurations are assembled
1.2
The Test Fixture
The test fixture is mounted on a resilient base (Fig. 1.1) that reduces the noise floor to a mini
-
mum in a typical test situation. Foam plugs and grease (Fig. 1.1) are supplied to avoid sound
leakage along the cable.
• The test fixture head, made for optimizing the acoustic isolation.
• An acoustic cup and plug for testing the acoustic isolation (Fig. 1.1).
• A range of moulded-rubber KEMAR pinnae, e.g. for testing earplugs, can be fitted.
Fig. 1.1 Assembled 45CA Test fixture including Acoustic Plug and Acoustic Cup.
Blind Plug
GR1079
Resilient base
Neck
Head
Pedestal (neck + resilient base)
Two 1.5 mm Allen grub screws - must
ALWAYS be tightened when pedestal
and head are assembled
Cup
GR0974
Tube of
Sealing Grease
MI0016
2 x Foam Plug
GR1281