How to Conduct Noise Monitoring: Phone App vs Professional Survey
Almost every California facility that calls CDMS about noise has already done one thing: someone walked the floor with a sound meter app on their phone.
Almost every California facility that calls CDMS about noise has already done one thing: someone walked the floor with a sound meter app on their phone. Sometimes the safety manager. Sometimes the GM. Once or twice an HR person who got an employee complaint about the line being loud. They get a reading in the 80s or 90s, and that is usually the moment they pick up the phone.
The next question we hear is some version of the same thing: “Can I just use the app, or do I need someone out here?” The honest answer is that the app is useful, but not for the document Cal/OSHA expects to see. Here is the difference, and what to have ready when you decide a professional noise survey is the right call.
What a Phone App Can Actually Tell You
Phone sound meter apps measure sound pressure level in dBA using the phone’s microphone. For a quick walk-through, they can answer one useful question: is the floor loud enough that you should look into formal monitoring? If the app reads 70 dBA at a normal voice from three feet away, you probably do not have an 85 dBA action-level problem. If the app reads in the high 80s near a grinder, packaging line, or compressor, you almost certainly do.
That is the legitimate role of a phone app: a pre-screen. It tells you whether the question is worth asking. It cannot answer the question itself.
Why Cal/OSHA Will Not Accept App Data
Cal/OSHA’s noise standard (Title 8 CCR §5096) does not list a single approved app. The standard expects measurements taken with a dosimeter or sound level meter configured to specific settings, calibrated against a reference acoustic calibrator before and after each field use, and worn or placed in a way that captures the employee’s actual exposure across a representative shift.
A phone microphone fails on every count. It is not calibrated to a known reference. It uses the phone’s microphone hardware and signal processing, both of which vary between models and operating system versions. It does not let you set the 80 dB threshold, 90 dB criterion, 5 dB exchange rate, A-weighting, and slow response that the standard requires. And it is not worn at the employee’s collar near the ear for the full shift, which is how a personal time-weighted average (TWA) is built.
When a Cal/OSHA inspector asks for noise monitoring records and what comes back is a screenshot from a phone app, the inspector treats that as no data. The facility is then directed to produce a defensible survey, usually on a deadline. For the regulatory background and the action-level numbers behind this, see our OSHA noise monitoring requirements guide.
What a Professional Noise Survey Delivers
A professional noise survey produces the record Cal/OSHA, an insurer, or a corporate safety office will accept. The table below lays the two side by side.
| Attribute | Phone Sound Meter App | Professional Noise Survey |
|---|---|---|
| Equipment | Phone microphone, varies by model | Calibrated personal dosimeter and/or Type 2 sound level meter |
| Calibration | None | Calibrated to 94.0 ±0.5 dB before and after each field use |
| Settings | Fixed by the app, often unclear | Threshold 80 dB, criterion 90 dB, 5 dB exchange rate, A-weighting, slow response (per Title 8 §5096 Appendix A) |
| Placement | Held by the person walking around | Worn at the employee’s collar near the ear for a 6–8 hour representative shift |
| What it outputs | Instantaneous dBA reading | Personal 8-hour TWA compared to the 85 dBA action level and 90 dBA permissible exposure limit |
| Field notes | None | Documented operations, employee tasks, equipment running, whether the day was representative |
| Use it for | Deciding whether to scope formal monitoring | Cal/OSHA compliance, hearing conservation program triggers, audit-file documentation, litigation defense |
A useful way to think about it: the app tells you whether you have a problem. The survey tells you who has the problem, how big it is, and what the regulation requires you to do about it.
When the Phone App Is Useful
The app is not the enemy. Used the right way, it saves time and money. Three places it earns its keep:
- Deciding whether to call at all. If your loudest area is reading in the high 70s on the app, you may not have an action-level issue. That is worth knowing before you scope a project.
- Identifying which roles to monitor. When we walk a facility for noise scoping, we often ask the safety manager which equipment and which roles they have already measured with their phone. That informally narrows the sampling plan from six positions to three.
- Tracking change between formal surveys. Once you have a defensible baseline, an internal phone-app check after new equipment or a layout change tells you whether to commission a re-survey. The app reading does not replace the new survey, but it tells you whether you need one.
What the app cannot do is satisfy Cal/OSHA, prove compliance to a corporate office, support a hearing conservation program decision, or hold up in litigation. For those, the survey is the answer.
What to Have Ready When You Call
When the phone-app reading tells you formal monitoring is warranted, the scoping call goes faster if you have the basics in front of you. The information we ask for on the first call, in plain terms:
Number of employees potentially exposed.
Not the whole facility headcount. The employees in the loud areas. A real intake example: “29 employees who work around aircraft.”
Shift pattern.
Single shift, multiple shifts, 24/7? A single first-shift survey will not represent a 24/7 operation. We may need a multi-shift design.
Specific roles or areas of concern.
Production line operators, packaging, machine shop, warehouse forklift, generator room. Be specific. “It’s loud in there” is a starting point. “The roaster operator and the packaging operator” is a scope.
Whether roles rotate or stay put.
A dedicated role is easier to sample than a worker who rotates through five stations each shift. We adjust the methodology accordingly.
What triggered the call.
Cal/OSHA visit, employee complaint, insurance carrier request, new equipment, corporate safety program. The trigger shapes what level of defensibility the report needs.
Your phone-app readings, if you have them.
Approximate dBA at each area and roughly when you took it. This helps narrow the sampling plan.
Facility location and access.
Address, the contact person for site access, and whether monitoring needs to happen during typical production hours.
For the broader picture of how this fits into your facility’s industrial hygiene services program, see our pillar guide. For what the deliverable itself looks like, see our noise (sound) monitoring service page.
Is the complaint coming from outside the building? See how workplace and property-line noise surveys differ →
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BSY started working with CDMS last year after our in-house EHS person departed the company. CDMS reviewed our existing operational permits as well as any additional Federal, State and Local regulations that could apply and helped us to create a comprehensive compliance calendar to track regulatory deadlines and submittal due dates. The CDMS team does an excellent job of tracking everything and can be relied upon to complete the forms accurately and assist with submittals, allowing me to focus on our business.
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