Maintenance
Part of Inside desk noise testing: what happens at each stage
Keeping a noise measurement repeatable over time
Instruments drift, rooms change and phones get replaced. What to check, what to record, and how to keep a year-old reading worth comparing against.
A single measurement is a snapshot. A series is evidence, and a series only holds together if the method stays fixed. This is the upkeep that keeps old readings usable.
What to take away
- Calibration is not one event. Professional practice uses periodic checks plus checks around each use.
- Record the instrument, not just the number. A phone replacement invalidates the series.
- Re-baseline whenever the room, the equipment or the instrument changes.
- The reason to keep any of this going is hearing, which does not recover.
What professional practice looks like
The standard worth copying is set out in the OSHA technical manual chapter on noise measurement and instrument care. It requires all instruments to be calibrated according to the manufacturer's instructions, and describes two distinct kinds of calibration: periodic factory-level calibration, typically annual, which produces a certificate and a dated sticker, and pre- and post-use calibration around each measurement session. The acoustical calibrators themselves are calibrated annually. It also treats the mundane things as part of the method, including battery condition and storing the instrument in its own case.
You are not running an inspection. The transferable idea is that a check before and after each session catches the errors that a yearly check cannot.
A home version of the same discipline
- Before each session: note the phone, the app version, and any case.
- Take a thirty second background reading before the test and after it.
- If the two background readings differ by more than a decibel or two, discard the session.
- Keep the tape marking the microphone position, and check it is still there.
- Photograph the setup once, so a year later you can reproduce it.
What invalidates an old reading
| Change | Effect | What to do |
|---|---|---|
| New phone | Different microphone and audio path | Re-baseline everything |
| App update | Possible change to weighting or averaging | Re-baseline, note the version |
| Room furniture moved | Different reflections | Re-baseline |
| New appliance or ventilation | Different background | Re-take background, may be fine |
| Different time of day | Different background | Keep to the original slot |
Why keep it up at all
Because the underlying reason is not the number. Hearing loss is common, gradual and permanent, and the World Health Organization records in its fact sheet on deafness and hearing loss that over 5 percent of the world's population, around 430 million people, need rehabilitation for disabling hearing loss, that the figure is projected to exceed 700 million by 2050, and that over a billion young adults are at risk of permanent avoidable hearing loss from unsafe listening. A desk is not an industrial hazard. The headphones people use to escape a noisy desk can become one.
The minimum viable routine
Once a year: repeat the standard measurement, check the microphone position, note any change to the phone or room, and read back last year's entry. Ten minutes. The judgment about whether measuring is worth it at all is in is measuring your desk noise worth the trouble, and the stage-by-stage method is in what happens at each stage.
Common questions
Can I calibrate a phone app? Some apps allow an offset to be entered against a known source. Without a calibrator that offset is a guess, so change it rarely and record when you did.
How long should I keep records? As long as the situation lasts. In a tenancy dispute a dated series from before the complaint is the most useful document you can have.
Does the app updating really matter? It can. Note the version each time so that an unexplained step change has a candidate cause.
What if I lose the marked position? Re-establish it from the photograph and treat the first new reading as a fresh baseline rather than a continuation.
