The continuous hum of a living room AC is usually around 45 dBA—open Noise Detector Pro to verify it instantly

Noise Detector Pro is a sound level analysis tool that runs directly in your browser. It uses your device's microphone to capture ambient sound in real time, implementing A, C, and Z frequency weightings according to the IEC 61672 standard. It synchronously calculates the Sound Pressure Level (SPL) and plots a 48-band FFT spectrum. Click "Start Monitoring" and allow microphone access; the main dial will instantly display the decibel reading for the current weighting, while the spectrum area on the right shows the energy distribution from 20 Hz to 20 kHz. When we casually ask "how many decibels," we usually mean A-weighting (dBA), which mimics the human ear's sensitivity to different frequencies. C-weighting retains more low frequencies, making it suitable for evaluating heavy bass or explosions. Z-weighting applies no frequency correction and is commonly used for audio testing and scientific research. This tool is not hardware-calibrated; values are for reference only and cannot replace legally certified measuring instruments.

How to Use

Open the page, and you will see a circular dial in the center, a weighting toggle area in the top right, and a spectrum graph below. Click the "Start Monitoring" button first, and when the browser prompts for microphone permissions, select "Allow".
The default weighting is dBA, which aligns with the frequencies most sensitive to adult ears. If you need to evaluate heavy bass or full-frequency characteristics, click the "dB(C)" or "dB(Z)" buttons in the toggle area. The numbers and scale on the main dial will instantly switch to the corresponding weighting.
The number on the dial represents the current ambient decibel level, refreshing every 0.1 seconds. The horizontal axis of the spectrum graph is frequency, and the vertical axis is relative energy. You can click the "Log/Linear" button to switch the scale and observe whether the noise is concentrated in low, mid, or high frequencies.
To record changes over time, click "Start Recording". You can enter a description in the pop-up note box (e.g., "Bedroom night background"), then click "Stop Recording" to end. During recording, the tool captures dBA, dBC, and dBZ data sets at a rate of 10 times per second.
After recording, click the "Records" button in the top right to view your saved list. Select a record, and you can click "Export Summary CSV", "Export Raw Sampling CSV", or "Export Full JSON" to download the data to your device.

Practical Example: Measuring a Neighbor's Power Drill Noise

On a weekend morning, your neighbor's renovation drill is running non-stop. Let's use Noise Detector Pro to collect some objective data.

Open the page, click "Start Monitoring", and grant microphone access. The main dial shows the ambient background noise is about 38 dBA.
When the drill suddenly starts, ensure you are on "dB(A)". The reading quickly jumps to 86 dBA. A sharp peak appears around 2 kHz on the spectrum graph, which matches the high-frequency noise characteristics of a power drill.
To keep a record, click "Start Recording" and enter "Neighbor's drill 10:15 AM" in the notes. The system begins logging dBA/dBC/dBZ at a 10 Hz sampling rate.
After 3 minutes of continuous monitoring, the drill stops, and the background noise drops back to 40 dBA. Click "Stop Recording", and this record is automatically saved locally.
Open the records list and find the entry you just made. Click "Export Raw Sampling CSV" to get a spreadsheet file containing timestamps, dBA, dBC, and dBZ. Opening it in Excel reveals a peak of 86 dBA and an average of about 72 dBA, clearly exceeding recommended daytime indoor limits.

How to Interpret Results: Decibel Range Reference

Decibels are a logarithmic unit; for every 10 dB increase, sound pressure multiplies by approximately 3.16. Below is a reference for common environments measured with A-weighting (uncalibrated, for relative comparison only).

dBA Range	Typical Environment	Subjective Perception
20-30	Quiet bedroom, recording studio	Extremely quiet, whispering
30-50	Library, quiet office	Quiet, normal conversation is clear
50-65	Next to a washing machine, busy street	Conversation is okay, slightly noisy
65-75	Vacuum cleaner, city thoroughfare	Noticeably loud, need to raise voice to converse
75-85	Heavy truck passing, near a power drill	Very loud, long-term exposure may damage hearing
85+	Rock concert, angle grinder	Can cause hearing damage in a short time

If your recording average consistently exceeds 70 dBA, consider taking noise reduction or protective measures. Using the raw sampling from the exported data, you can further calculate the Equivalent Continuous Sound Level (L_Aeq) to assess exposure risks more scientifically.

Typical Use Cases

Home Environment Assessment: Is the operating noise of your AC, ventilation system, or refrigerator affecting your sleep? Launch Noise Detector Pro, select A-weighting, and take a steady-state reading 1 meter away from the appliance. If it exceeds 45 dBA, it might disrupt sleep, and you can provide this value to the installer as reference.
Office Noise Compliance: Background noise in open-plan offices often disrupts focus. Use the tool to record for 10 minutes at your desk, export the raw CSV, calculate L_Aeq, and compare it against the GB/T 12349 recommended office noise limits to help propose improvements