Daily Calibration Fails With No-Response (NR) Errors

What's happening

Every day before testing, your system runs a check against the bio-acoustic simulator (BAS) to confirm the audiometer's output is still accurate — this daily check is part of what keeps your testing compliant with OSHA's occupational noise standard, 29 CFR 1910.95. "NR" (No Response) means the BAS didn't respond to two stimulus presentations at the audiometer's maximum output. "MR" (Multiple Response) means it registered more than one response to a single tone. Benson describes it two ways, and both are worth knowing because they look identical on a daily check: formally it is more than one response to a single stimulus, and the prompt shown to a live subject phrases it as pressing the hand switch when no tone is present. Either way it is responses arriving that don't line up one-to-one with tones. Both point to something in the connection between the audiometer and the BAS, not a problem with the subject or the test itself.

An occasional NR while things are warming up isn't unusual. But if it's failing repeatedly — several times in one morning — don't just cancel out and restart over and over. Work through the list below, and save or print the calibration log as you go. If the unit ends up needing service, that log is the clearest evidence of the actual pattern.

Check this before anything else: is the response switch unplugged?

This is the most common cause of a daily check throwing NR, and it is a ten-second fix that costs nothing. For a daily calibration check, the response switch must NOT be plugged into the Bio-Acoustic Simulator. For subject testing it does get plugged into the simulator's RESPONSE jack. Those are two different configurations, and it is easy to run the morning check with the booth still set up the way it was left after yesterday's testing.

The reason matters, because it explains why the symptom looks like broken hardware. Benson's manual states that when the response switch is inserted into the simulator, internal switching removes the simulator from the circuit — that is deliberate, so the simulator can stay installed permanently without affecting subject tests. But during a daily check it means the BAS is switched out of the very circuit you are trying to check. The audiometer presents its tones, nothing is there to answer them, and you get No Response at every frequency.

1. Unplug the response switch from the Bio-Acoustic Simulator and run the daily check again. If it passes, that was the whole problem — no cord to buy, no loaner to request.
2. Plug it back into the simulator's RESPONSE jack before you test anyone. Subject testing needs it connected; leaving it out means the subject has no way to respond.

If the check still fails with the response switch disconnected, then work through the list below.

If it still fails, try these in order

1. Unplug and replug the short cord connecting the audiometer to the BAS. This is a short cable that also carries power between the two units, so reseating it resets that connection — and clears a real share of these on its own.
2. Watch the BAS's response light while you do this. It should flash briefly when that cord is disconnected and reconnected, and light steady when the response button is pressed. If it doesn't react at all, note that — it matters for the steps below.
3. Check whether the failure is on one side only. If it's consistently one ear or one channel throwing NR, that points more toward the headphone cord or that same short BAS cord than toward the whole unit being bad.
4. Reseat the headphones and check the tension. Make sure the cushion sits flush and the headband is pulled all the way down. A cushion sitting slightly off can cause an intermittent failure that looks exactly like a connection problem.
5. Swap the short cord between the audiometer and BAS. This has turned out to be the single most common real fix. It's a 1/4-inch auxiliary patch cable, about 6 inches long — sometimes sold as a "guitar patch cord" — and the correct one has a single black band around the connector, not two (a two-band version is a different, powered/stereo type and won't work correctly here). It's a same-day option through any general electronics retailer, and it's worth trying before anything more involved.
6. If that doesn't fix it, try swapping the whole BAS unit if you have a spare, or flip which cord goes to which side. This helps separate a BAS fault from a fault further down the chain.
7. If the booth has a patch panel, bypass it. Disconnect the BAS/audiometer cabling and connect it directly rather than through the panel. A misaligned or faulty patch-panel connection has been the actual cause behind what looked like a dead unit more than once.
8. Don't assume a BAS swap alone fixed it. In more than one case, replacing the BAS entirely — even with a new unit — didn't resolve the failure, because the real fault turned out to be the short cord or, in one instance, stripped screws on the headphone connector that needed the transducer itself replaced. Keep watching the daily log for a few more days after any swap before calling it fixed.

If the signal runs through a booth patch panel

Most booth patch panels pass straight through the wall — each port on the outside connects to the port in the same position on the inside. That gives you two extra things to check when the daily won't pass or no sound comes through:

1. Confirm the ports line up. The cable outside and the cable inside must be in corresponding holes — same position on both faces of the panel (some panels number the ports; on unnumbered panels, match the physical position). A cord moved to a different outside port while the inside stayed put looks exactly like a dead channel.
2. Swap the affected channel to a different port pair. Move that cable to another port — on both sides of the wall, keeping them matched — and run the daily again. Panel contacts get dirty over time, and a single bad port causes static, one-ear failures, or NR on an otherwise healthy setup. If the problem clears on the new pair, the old port is the fault.
3. Swap or reseat the response cord. The response switch cord plugs into the booth's response port and is the same type of cord as the audiometer side — swap them to isolate a kinked or failing cord. On CCA-200mini setups, the orange and red indicator lights next to the response port tell you whether that connection is live.
4. Still stuck? Bypass the panel entirely (direct cable, as above). If it passes bypassed but fails through the panel on every port pair, the panel or booth wiring is the fault — that's a call to Foster, not a field fix.

If it still won't pass

Save a few days of the calibration log before you call us. It's the most useful thing you can hand over — it shows whether the failure is happening at one frequency or several, one side or both, and whether it's every test or intermittent.

If a subject's reference reading at one frequency looks unusually low or high but comes through completely consistently across repeated tests, that pattern can sometimes be worth factoring in going forward — but that's a decision we make together using your logged data, not something to adjust on your own in the field.

When to call us

• You're seeing actual threshold shifts on real tests, not just the daily check — stop testing and call rather than continuing to run people through a booth that's already failing its own calibration.
• Anyone reports crackling, popping, or a "short" sound in either ear.
• You've swapped the short cord and the headphone cords, checked both sides, and it's still failing.
• The BAS response light doesn't react at all to a plug/unplug or a button press.

We can usually get a loaner out the same day or next day if the unit needs to come in.