Ultrasonic Frequency Detector
This ultrasonic frequency detector is a specialized tool for high-frequency sounds from 15–24 kHz. Identify CRT monitor whine, ultrasonic pest deterrents, switching power supply noise, and mosquito ringtones. Whether you are tracking down a high pitched noise in your home or verifying an ultrasonic sound source, the tool tests your microphone’s upper frequency limit and helps you discover your personal hearing cutoff.
Ultrasonic Frequency Detector Tool
| Age Group | Typical Upper Limit | Notes |
|---|---|---|
| Under 18 | 17.4 – 20 kHz | Can hear mosquito ringtones |
| 18 – 24 | 16 – 18 kHz | Most young adults |
| 25 – 34 | 15 – 17 kHz | Gradual high-freq loss begins |
| 35 – 44 | 14 – 16 kHz | Noticeable decline |
| 45 – 54 | 12 – 15 kHz | Presbycusis common |
| 55 – 64 | 10 – 13 kHz | Significant high-freq loss |
| 65+ | 8 – 11 kHz | Variable; hearing aids may help |
| Time | Frequency | Level dB | Likely Source |
|---|
| Time | Peak kHz | Level dB | Source |
|---|
How to Use the Ultrasonic Frequency Detector
Start Listening
Click "Start Listening" and grant microphone access. The tool immediately shows your microphone’s sample rate and maximum detectable frequency. A 44.1 kHz sample rate mic can detect up to ~22 kHz; a 48 kHz mic up to ~24 kHz.
Read the Ultrasonic Display
The large kHz display shows the strongest frequency detected in the 15–24 kHz range. The source identification card matches detected frequencies against known ultrasonic sources like CRT monitors, pest deterrents, and SMPS converters.
Check Your Microphone Capability
The Microphone Capability section shows your hardware’s actual upper frequency limit. The Nyquist theorem means your mic’s max detectable frequency is half its sample rate. The meter visualizes how much of the ultrasonic range your mic covers.
Test Your Hearing
Click "Test My Hearing" to run an ascending tone test. The tool plays tones from 8 kHz upward — press "I Can Still Hear It" to advance. When you can no longer hear the tone, press "I Can’t Hear This" to record your personal hearing cutoff and compare with age-based averages.
Enable Alert Mode & Export
Toggle Ultrasonic Alert to receive visual notifications whenever ultrasonic activity is detected. The alert log records each event with timestamps. Use Export CSV to download your full detection history.
Understanding Your Results
Frequency Display
The main display shows the peak frequency in the 15–24 kHz ultrasonic range. Frequencies are shown in kilohertz (kHz) for readability. A strong, steady reading near a known source frequency (e.g., 15.7 kHz for CRT) is a reliable identification.
Source Identification
The source card matches your detected frequency against a database of common ultrasonic emitters. Multiple sources may overlap in frequency, so the tool selects the closest match based on the narrowest matching range. If no known source matches, the raw frequency is displayed.
Microphone Capability Meter
Your microphone’s effective upper limit depends on its sample rate and physical hardware. The capability meter shows what portion of the ultrasonic range your mic can actually capture. If your mic’s limit is below the frequency you’re looking for, you will need higher-quality audio hardware.
Technical Background
Nyquist Theorem and Sample Rate
The Nyquist–Shannon sampling theorem states that a digital audio system can only capture frequencies up to half its sample rate. A microphone operating at 44,100 Hz (CD quality) has a theoretical maximum of 22,050 Hz. At 48,000 Hz, the limit rises to 24,000 Hz. This is why the sample rate displayed by the tool is critical — it directly determines whether you can detect frequencies in the ultrasonic range at all.
Microphone Hardware Limitations
Even with a sufficient sample rate, many consumer microphones have a frequency response that rolls off well below the Nyquist limit. Built-in laptop microphones typically attenuate significantly above 16–18 kHz. MEMS microphones in phones may reach 20 kHz but with reduced sensitivity. For reliable ultrasonic detection, a measurement microphone or high-quality condenser mic with a flat response to 20 kHz+ is recommended. The tool’s mic capability test plays reference tones and checks whether the microphone can pick them up, giving you a practical measurement rather than relying on specifications alone.
Common Ultrasonic Sources
CRT televisions and monitors emit a characteristic 15,734 Hz whine from their horizontal scanning circuitry — the NTSC horizontal line rate. Electronic pest deterrent devices typically operate between 18–22 kHz, above the hearing range of most adults but detectable by younger people and many animals including dogs and cats. Switched-mode power supplies (SMPS) can produce audible and near-ultrasonic noise around 20 kHz from their switching oscillators, especially when under light load or malfunctioning; this is sometimes called coil whine or transformer whine in consumer electronics. The "mosquito ringtone" at 17.4 kHz exploits presbycusis — age-related high-frequency hearing loss — so that most adults over 25 cannot hear it, while teenagers still can. You can also use the audio spectrum analyzer to view the full broadband frequency content from any source when narrowing down an unknown ultrasonic noise. Understanding these sources helps you identify unexpected high-frequency sounds in your environment.
Frequently Asked Questions
What frequency range does this tool detect?
This tool focuses on the 15–24 kHz ultrasonic range. While the human hearing range nominally extends to 20 kHz, many ultrasonic sources operate slightly above or below this boundary. The tool analyzes FFT bins in this specific range for detailed detection.
Why can't my microphone detect frequencies above 20 kHz?
Your microphone’s maximum detectable frequency is limited by its sample rate (Nyquist theorem: max frequency = sample rate / 2). A 44.1 kHz mic caps at ~22 kHz. Most built-in mics also have hardware roll-off above 16–18 kHz. Use an external condenser mic for best results.
What is CRT whine and what frequency does it produce?
CRT (cathode ray tube) televisions and monitors produce a characteristic 15,734 Hz whine from their horizontal deflection circuitry. This frequency corresponds to the NTSC horizontal scan rate. PAL systems use 15,625 Hz. Many people — especially younger individuals — can hear this as a high-pitched squeal.
How does the hearing limit test work?
The test plays ascending pure tones starting at 8 kHz, increasing in steps. You click "I Can Still Hear It" to advance to the next frequency. When you can no longer hear the tone, click "I Can’t Hear This" to record your cutoff. The result is compared against age-based hearing averages. Use headphones for the most accurate result.
Can ultrasonic pest deterrents be detected with this tool?
Yes. Most electronic pest deterrents operate between 18–22 kHz. If your microphone’s sample rate is at least 44.1 kHz (nearly all modern mics), you can detect these devices. The source identification card will label the detected frequency accordingly.
What is the "mosquito ringtone" frequency?
The mosquito ringtone is a 17.4 kHz tone designed to be audible only to people under about 25 years old. It exploits age-related hearing loss (presbycusis) that naturally reduces sensitivity to high frequencies. This tool can detect and identify it even if you can’t hear it.
Is my audio data safe?
All processing runs 100% in your browser. No audio is recorded, stored, or transmitted. The tool works offline once loaded.
Can switching-mode power supplies (SMPS) really cause audible or near-ultrasonic noise?
Yes. Switched-mode power supplies operate by switching transistors on and off at frequencies typically in the 20–100 kHz range. When a supply runs at light load or develops coil vibration, the switching frequency can fall into the near-ultrasonic or even audible band. Younger people may perceive this as a faint high-pitched whine. This tool can locate the dominant peak frequency, helping you identify a faulty charger, laptop brick, or LED driver as the culprit.
What microphone should I use for accurate ultrasonic detection above 18 kHz?
Built-in laptop and phone microphones typically roll off above 16–18 kHz, making them unreliable for detecting frequencies near 20–22 kHz. For consistent results above 18 kHz, use an external USB condenser microphone or a professional measurement microphone rated flat to 20 kHz or beyond. The tool’s microphone capability meter tells you exactly how far your current hardware can reach before you rely on any reading.
How does age-related high-frequency hearing loss (presbycusis) affect what I can hear?
Presbycusis is the gradual loss of sensitivity to high frequencies that starts in early adulthood. The outer hair cells in the cochlea responsible for detecting high-pitched sounds deteriorate over time. By age 25 many people can no longer hear the 17.4 kHz mosquito ringtone; by 40 the typical upper limit drops to around 14–16 kHz. The hearing-limit test on this page lets you measure your own personal cutoff and compare it with age-group averages.
Can I use this tool to analyze a pre-recorded audio file instead of live microphone input?
Yes. The Analyze Audio File section accepts WAV, MP3, OGG, and FLAC files. The tool runs the same 15–24 kHz FFT analysis on the uploaded recording and reports the peak frequency and most likely source. Note that lossy formats like MP3 often cut off content above 16–20 kHz depending on the encoder settings, so lossless WAV or FLAC files give more reliable results for ultrasonic content analysis.