Description:

Weighing 16.5 lb in its 15.5 × 12.5 × 6.3 in case, the MA 39 brings ANSI-S3.6-compliant threshold testing to schools and factories alike. Two oversized rotary dials select octave or inter-octave frequencies from 125 Hz to 8 kHz and presentation levels from –10 dB HL to 110 dB HL (mid-band). Operators toggle continuous, pulsed or 3 Hz warble tones, while a front-panel indicator confirms output routing to TDH-39 circumaural phones or optional inserts. Frequency accuracy is held within ±3 %, with total harmonic distortion < 3 % at any setting. Powered by an external 120 V adapter or 12 V DC supply, the solid-state attenuator delivers stable outputs in booths or mobile vans. All controls give tactile detents—ideal for low-light test rooms—and the metal housing survives constant travel.

Economic Advantage:

Many conservation programs relied on bulky clinical audiometers; the MA 39’s suitcase form lets one technician screen a remote workforce without hiring third-party vans. Its zero-maintenance analog circuitry avoids annual calibration drift seen in digital handhelds, driving per-test costs to pennies over a decade of use.