ER-3A Insert Earphones:
• approximate the TDH-39, -49, and -50 response at the eardrum
• are calibrated in a 2-cc coupler
• provide 30+ dB external noise exclusion
• provide noise exclusion equivalent to a single-wall booth
• provide 70+ dB isolation between ears, reducing the need for masking
• improve test/retest reliability compared to supra-aural earphone
• eliminate collapsed ear canal errors
• simplify RECD (Real-Ear-to-Coupler-Difference) measurements
Foam eartips developed for ER-3A insert earphones are produced with constant dimensions to ensure
proper calibration and test accuracy. To accommodate differences in ear canal size, there are three sizes
of foam eartip (small, medium and large). To obtain accurate test results, the following dimensions must
1. The length from the end of the eartip to the connection at the end of the earphone tube should
be 22 mm (Figure 1). Do not cut the black tubing that connects the foam eartip to the sound tube.
2. The diameter from the end of the eartip to the connection at the end of the earphone tube should
be 1.93 mm (Figure 1).
3. Insertion depth should be 14-15 mm into the ear canal, which is achieved when the edge of the
foam eartip is 2-3 mm inside the entrance to the ear canal (Figure 2).
• Do not cut the sound tube itself. A change of 10 mm in the length of the sound tube will result
in a change of the frequency response by 0.5 dB at some frequencies.
• Replace the sound tubes (ER3-04) if they crack or harden.
• Do not reuse foam eartips.
Foam eartips are recommended for most uses; however, immittance probe tip adapters (ER3-06) can
be used with commonly used immittance eartips. When using immittance adapters, calibration will be
maintained if the eartip is seated on the adapter so that the opening of the eartip is flush with the tip
of the adapter (Figure 3). No data are available on the interaural attenuation or noise exclusion of
INSTRUCTIONS FOR USE