How to compare noise levels before and after soundproofing

You have added seals, curtains, panels, or another soundproofing measure. Now you want to know whether less noise is getting through. A quick reading can help, but only if you compare the same sound under similar conditions.

The Noise Meter uses your device’s microphone to show a noise level in decibels. Use it to compare readings before and after, not as a calibrated measurement for legal or professional sound limits.

Compare noise levels

1. Open the Noise Meter on the device you plan to use for both tests. Allow microphone access when your browser asks.
2. Choose one position for the microphone, such as a marked spot beside the window or in the middle of the room. Keep the device at the same height and facing the same direction each time.
3. Measure before soundproofing if you have not started yet. Wait for the reading to settle, then write it down. Take several readings, for example three readings of about 30 seconds each, and note the typical level.
4. Make the soundproofing change, then test again from the same position. Keep doors and windows in the same state, and use the same device and browser.
5. Compare the typical readings, not just the loudest moment. Also note what the sound was like, such as steady traffic, voices, or a fan, and whether it seemed quieter to you.

A repeatable sound source makes the comparison more useful. If you can do so safely, use the same source at the same location and volume for both tests. For outside noise, choose a period when traffic or other noise is reasonably steady. Wind, passing trucks, voices, and changing activity can shift the reading more than the soundproofing did.

What the result means

The reading is lower after soundproofing

Less sound reached the microphone during the second test. A consistent drop across repeated readings is a good sign, especially if the room also sounds quieter. The reading does not identify which gap or material made the difference, so check the areas you changed one at a time if you need to find the most effective improvement.

The readings are about the same

The change may be smaller than the variation in the room, or the sound may be entering through another route. Check whether the source and conditions really matched. Also consider whether the work reduced echo inside the room rather than noise coming through the wall or window.

The reading is higher afterward

This does not necessarily mean the soundproofing made things worse. A louder passing vehicle, a different microphone position, or a changed room condition can raise the result. Repeat the comparison with the original setup and take multiple readings before drawing a conclusion.

The number jumps around

Noise that changes over time will produce changing readings. A measurement app also relies on the microphone built into your device, which may adjust its sensitivity automatically. Treat the value as a relative comparison from the same device, not as an exact sound pressure level.

How to fix an unreliable reading

1. Use the same device and microphone. Phones and computers can give different readings because their microphones and sound processing differ. Do not compare one device before the work with another device afterward.
2. Keep the microphone still. Place the device on a stable surface instead of holding it. Mark the position and direction so you can repeat them. Avoid covering the microphone opening with a hand, case, or fabric.
3. Control the room conditions. Keep windows, doors, ventilation, and nearby appliances in the same state. Turn off speech and music during the measurement unless one of those is the sound you are checking.
4. Allow microphone access. If the meter cannot read sound, check the browser’s permission beside the address bar and allow microphone access. In Windows 11, open Settings › Privacy & security › Microphone. On macOS, open System Settings › Privacy & Security › Microphone. On iPhone, check Settings › Privacy & Security › Microphone. On Android, check Settings › Apps › your browser › Permissions › Microphone, noting that menu names vary by device.
5. Repeat at a quieter time. If the sound source keeps changing, wait for steadier conditions and take several readings. Compare the typical values rather than relying on one peak.

Why soundproofing may not change the reading much

Sound can travel through more than the surface you treated. It may come through gaps around doors and windows, vents, a ceiling, a floor, or connected walls. A small opening can undermine work on a much larger area, so inspect seals and edges as well as the main surface.

Soundproofing and acoustic treatment do different jobs. Sealing gaps and adding suitable mass can help reduce sound passing between spaces. Foam or fabric panels mainly reduce reflections and echo inside a room. They may make speech sound clearer without greatly reducing the noise coming through an exterior wall.

Decibels use a logarithmic scale, so a difference in the number does not correspond to the same percentage change in perceived loudness. A change of 3 dB represents about half the sound energy, but may be subtle to hear. A reduction of around 10 dB is often perceived as roughly half as loud, though the sound itself and the room affect what you notice.

For a fair check, repeat the measurement with the same device, source, and microphone position, and trust a consistent pattern more than one reading.