Peak Frequency Detector
Use this peak frequency detector to instantly find the loudest frequency in any sound. See the peak Hz value in a giant display, view the top 5 strongest frequencies ranked by level, track peak hold across your session, and get instant noise diagnosis cards — all processed locally in your browser.
Peak Frequency Detector Tool
Or drop an audio file here to analyze —
MP3, WAV, OGG, FLAC — max 50 MB
| # | Frequency | Note | Band | Level (dB) |
|---|---|---|---|---|
| Start listening to detect peaks | ||||
| Time | Peak Hz | Note | Band | dB |
|---|
How to Use the Peak Frequency Detector
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Start Listening
Click "Start Listening" and grant microphone permission. Choose your preferred microphone from the dropdown. The tool begins scanning for the loudest frequency immediately.
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Read the Giant Hz Display
The large number shows the single strongest frequency in your audio signal, along with its musical note name and frequency band classification (sub-bass, bass, mid, treble, etc.).
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Check the Top-5 Peaks Table
Below the main display, the Top 5 Strongest Frequencies table shows additional peaks with their Hz, note, band, and level. This helps identify all significant frequencies in complex sounds.
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Review Noise Diagnosis
The Noise Diagnosis card automatically matches common noise sources (mains hum, HVAC, ground loop, etc.) and provides actionable troubleshooting advice based on the detected peak frequency.
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Copy or Export Results
Use 📋 Copy Peak Frequency for instant clipboard access, or 💾 Export CSV to download your full session history for documentation.
Understanding Your Results
Peak Frequency (Hz)
The main display shows the single loudest frequency component in the audio signal — the quickest way to find peak frequency in any live or recorded sound. This is the frequency with the highest amplitude in the FFT spectrum. As a real-time peak frequency analyzer, it uses parabolic interpolation to refine the reading beyond the raw FFT bin resolution for sub-Hz accuracy. The tool also identifies the corresponding musical note (e.g., A4 = 440 Hz), giving context that is useful whether you are tuning an instrument or diagnosing an unwanted resonance. For a complementary view of overall signal amplitude, see the peak level analyzer.
Top-5 Peaks
The peaks table shows the 5 strongest frequency components ranked by amplitude. Each peak must be at least 100 Hz apart to avoid listing harmonically-related duplicates. This helps identify multiple noise sources or harmonic overtones in complex sounds. A buzzing electrical fault, for example, often shows a fundamental at 60 Hz and harmonics at 120 Hz, 180 Hz, and 240 Hz simultaneously.
Frequency Bands
Each frequency is classified into a standard audio engineering band: Sub-Bass (20–60 Hz), Bass (60–250 Hz), Low Mid (250–500 Hz), Mid (500–2k Hz), Upper Mid (2k–4k Hz), Presence (4k–6k Hz), and Brilliance (6k–20k Hz). The band energy bars show how energy is distributed across these ranges. This classification mirrors the standard equalizer band layout used in audio mixing and mastering workflows.
A-Weighting
When enabled, A-weighting adjusts the spectrum to match human hearing perception. Low and very high frequencies are de-emphasized because humans are less sensitive to them. This shows which frequency sounds loudest to you rather than which has the highest raw amplitude. A-weighted readings correspond to the dBA scale used by occupational noise regulations and consumer sound level meters, making this mode useful for workplace noise assessment context.
Noise Diagnosis
The tool includes a database of 30+ common noise signatures. When you need to answer the question "what frequency is this sound?", this feature delivers: when the peak frequency matches a known noise source (e.g., 60 Hz mains hum, 120 Hz ground loop, HVAC fan frequencies), it displays an identification card with the likely source and suggested fix. This makes it practical for audio troubleshooting — identifying hum, buzz, and tonal interference in recording setups, home studios, and live sound environments. To check overall noise floor levels across octave bands, try the noise floor analyzer.
Peak Hold
The Peak Hold value tracks the highest frequency detected during the entire session. This is useful for capturing transient peaks that appear briefly and might be missed on the live display. Combined with the session statistics (min, average, and max peak), it gives a complete picture of how the dominant frequency shifts over time — helpful for monitoring intermittent noise events.
How Peak Frequency Detection Works
As a loudest frequency finder, this tool works by transforming the audio signal from the time domain into the frequency domain. It uses the Fast Fourier Transform (FFT) to decompose the audio into its constituent frequency components and identify which one carries the most energy.
FFT Analysis
The Web Audio API's AnalyserNode computes the FFT in real time. With the default FFT size of 8,192
at a 48 kHz sample rate, the frequency resolution is approximately 5.86 Hz per bin. Increasing
the FFT size to 16,384 doubles the resolution to ~2.93 Hz, which is important for distinguishing closely-spaced
low-frequency noise sources (e.g., 50 Hz vs 60 Hz mains). The spectrum visualization is rendered
on a logarithmic frequency axis so low-frequency detail — where most environmental noise lives — is not
compressed out of view. You can also analyze audio files (MP3, WAV, OGG, FLAC) by dragging
them onto the upload zone, which is useful for offline recordings where a live microphone is not practical.
For the complementary pitch-focused view, the dominant frequency finder
applies additional filtering to isolate fundamentals.
Parabolic Interpolation
Raw FFT bins give discrete frequency values. To achieve sub-bin accuracy, the tool applies parabolic interpolation using the three bins around each peak (the peak bin and its two neighbors). This refines the frequency estimate to within ±0.5 Hz even with moderate FFT sizes.
A-Weighting Curve
The optional A-weighting filter applies the IEC 61672 frequency response curve, which approximates the sensitivity of the human ear at moderate listening levels. It attenuates frequencies below 500 Hz and above 6 kHz, boosting the mid-range where human hearing is most sensitive. This is the same weighting used in professional sound level meters (dBA).
Noise Source Matching
The diagnostic engine maintains a lookup table of common noise frequencies and their sources. When the peak frequency falls within a known range, the tool displays the likely source and a suggested remedy. This covers electrical hum (50/60/100/120 Hz), HVAC systems, fluorescent lighting, computer fans, and more.
Frequently Asked Questions
What is the difference between peak frequency and dominant frequency?
The peak frequency is the single frequency with the highest amplitude in the spectrum at any given moment. The dominant frequency typically refers to the fundamental pitch of a sound, which may not always be the loudest component (harmonics can be louder than the fundamental). This tool shows the raw peak — the loudest frequency, regardless of whether it's a fundamental or harmonic.
Why does my room show a 60 Hz (or 50 Hz) peak?
A persistent peak at 60 Hz (North America, Japan) or 50 Hz (Europe, Asia, Africa) is almost always electrical mains hum picked up by your microphone or audio cable. The harmonics at 120 Hz / 100 Hz are also common. This is normal and typically caused by electromagnetic interference from power lines, transformers, or unshielded cables.
What does A-weighting do and when should I use it?
A-weighting adjusts the readings to match how humans perceive loudness. Low-frequency sounds (below ~500 Hz) and very high frequencies (above ~6 kHz) sound quieter to our ears than mid-range sounds at the same level. Turn A-weighting on when you want to know which frequency sounds loudest to you, and leave it off when you want the raw, unweighted physical measurement.
How accurate is the peak frequency reading?
With the default FFT size of 8,192, raw accuracy is ±3 Hz. With parabolic interpolation enabled, accuracy improves to approximately ±0.5 Hz. For even better resolution, switch to FFT size 16,384. Accuracy also depends on your microphone quality and ambient noise conditions.
Can I use this to diagnose a humming or buzzing noise?
Yes — this is one of the primary use cases. Start listening in a quiet room with the humming noise present. The peak frequency display will show the exact Hz of the hum, and the Noise Diagnosis card will suggest the likely source (mains hum, ground loop, HVAC, etc.) with troubleshooting steps.
What is Peak Hold and how does it work?
Peak Hold remembers the highest peak frequency detected during your entire session. This is useful for capturing transient or intermittent sounds that appear briefly. It resets when you click the Reset button or refresh the page.
Is my audio data private?
Absolutely. All frequency detection and analysis runs 100% in your browser using the Web Audio API. No audio data is ever recorded, transmitted, or stored on any server. The tool works completely offline once loaded.
Can I detect peak frequency in an audio file, not just a live microphone?
Yes. Drag any MP3, WAV, OGG, or FLAC file (up to 50 MB) onto the upload zone, then click Analyze. The tool decodes the file entirely in your browser and runs the same FFT peak-detection pipeline, giving you the top-5 peaks, band classification, and diagnosis card without ever uploading the file to a server. This is useful for analyzing recordings of hum, hiss, or other tonal issues captured on a separate device.
Why does the peak frequency jump around instead of holding steady?
FFT peak detection reflects the actual content of the audio signal, which changes from frame to frame. If you want to capture the dominant steady-state frequency, use the Freeze button to lock the display at a moment of interest, or let the Peak Hold and session average accumulate over a longer window. Increasing the FFT size to 16,384 and adjusting the sensitivity threshold to filter quiet ambient fluctuations can also stabilize the reading for tonal noise sources.
What is the lowest frequency this tool can detect?
The tool covers the full audible spectrum from 20 Hz to 20 kHz, limited by your microphone's frequency response and the browser's Web Audio API sample rate (typically 44.1 kHz or 48 kHz). Most laptop microphones roll off significantly below 100 Hz, so a dedicated low-frequency or measurement microphone gives more reliable sub-bass readings below 60 Hz. The FFT bin at 20 Hz with an 8,192-point window at 48 kHz is representable, but microphone coloration dominates that range.
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