Proper insertion depth is necessary to achieve maximum ambient noise
attenuation and interaural attenuation. The graph below depicts interaural
attenuation as a function of insertion depth.
The described interaural
attenuation is obtained for each ear in which the E-A-RLINK
®
is fully inserted,
regardless of whether it is the “sending” ear or “receiving” ear.
2. Background Noise Reduction
A major benefit of the E-A-RTONE
®
Insert Earphone in combination with the
E-A-RLINK
®
disposable foam eartips is the reduction of background noise that
might interact with the presented pure tones and influence threshold
determinations. When E-A-RLINK
®
eartips are fitted to the subject according
to the instructions, the expected noise attenuation will typically exceed 30 dB
in the frequency region 125-8000 Hz. This additional attenuation will improve
test reliability in non-ideal environments and, in most cases, allow testing
down to 0 dB HL in a background noise level not exceeding 45 dB(A).
The current ANSI Standard (ANSI S3.1-1999) “Maximum Permissible
Ambient Noise Levels (MPANLs) For Audiometric Test Rooms” (Table 1
and Table 2) includes octave band and one-third octave band permissible
noise levels for both supra-aural and Insert Earphones. The ANSI octave
band MPANLs are presented below for standard earphones and also for
E-A-RTONES
®
with fully inserted E-A-RLINKS
®
.
4
-10
0
10
20
30
40
50
60
70
80
90
100
110
dB
125
250
500
1000
2000
4000
8000
Hz
Obtained Interaural Attenuation (E-A-RTONE 3A Data)
Full E-A-RLINK insertion in both ears
Shallow insertion in dead ear only
Shallow insertion in both ears
