Understanding Audio Frequency
TestTones generates these frequencies as pure, mathematically exact waveforms right in your browser — no app, no sign-up, and nothing uploaded. Before you start sweeping your subwoofer or finding the top of your hearing range, it helps to understand what frequency actually is. Measured in Hertz (Hz), frequency is the number of complete sound-wave cycles per second, and it's what your ear perceives as pitch. Getting comfortable with it is the key to using this tool for calibration, hearing checks, and tuning.
What is Frequency?
Sound travels through air as pressure waves. The frequency of a sound wave determines how many times these pressure variations occur per second. A higher frequency means more cycles per second, which we perceive as a higher pitch. The human ear can typically detect frequencies between 20 Hz and 20,000 Hz, though this range decreases with age.
Low Frequencies (20-250 Hz)
Low frequencies produce deep, bass sounds. You can often feel these as vibrations in addition to hearing them. Bass drums, bass guitars, and thunder operate in this range. Sub-bass frequencies below 60 Hz are more felt than heard.
Examples: Bass drum (60-100 Hz), Male voice fundamental (85-180 Hz)
Character: Deep, rumbling, powerful
Mid Frequencies (250-4000 Hz)
The mid-range contains most speech information and is where human hearing is most sensitive. Musical instruments' fundamental tones and harmonics occupy this space. The ear canal resonates around 3 kHz, making this region particularly prominent.
Examples: Human voice (300-3400 Hz), Piano middle C (262 Hz)
Character: Clear, present, articulate
High Frequencies (4000-20000 Hz)
High frequencies add brightness, air, and detail to sound. Cymbals, harmonics, and sibilance in speech occupy this range. Sensitivity to high frequencies typically decreases with age, a condition called presbycusis.
Examples: Cymbals (8-12 kHz), Consonant sounds (2-8 kHz)
Character: Bright, airy, detailed
How Frequency Relates to Musical Pitch
Musical notes correspond to specific frequencies. When we say "middle C," we mean a sound wave vibrating at 261.63 Hz. The relationship between frequency and pitch is logarithmic: doubling the frequency raises the pitch by exactly one octave. This is why A4 (440 Hz) and A5 (880 Hz) sound like the same note, just higher. To play pure musical tones by note name and build simple melodies, try ToneSynth.
Musical Notes and Their Frequencies (A4 = 440 Hz)
f = 440 x 2(n/12)
Where f is frequency in Hz, 440 is A4 reference, and n is semitones from A4
Hearing Range and Age-Related Hearing Loss
Human hearing spans approximately 20 Hz to 20,000 Hz at birth. However, this range naturally decreases with age, particularly at higher frequencies. This age-related hearing loss, called presbycusis, is a normal part of aging.
Young Adults (Under 25)
Can typically hear frequencies up to 17,000-20,000 Hz. Full hearing range with maximum sensitivity to high frequencies.
Typical Range: 20 Hz - 20,000 Hz
Adults (25-50)
Gradual decline in high-frequency sensitivity begins. Most people start losing frequencies above 15,000 Hz in their 30s.
Typical Range: 20 Hz - 12,000-17,000 Hz
Seniors (Over 50)
More noticeable high-frequency loss. Speech comprehension in noisy environments may become challenging.
Typical Range: 20 Hz - 8,000-12,000 Hz
Beyond age-related decline, exposure to loud sounds can cause permanent hearing damage at any age. Sounds above 85 dB (busy traffic, lawn mower) can cause damage with prolonged exposure. Sounds above 120 dB (concerts, sirens) can cause immediate damage. Protect your hearing by using earplugs in loud environments and keeping headphone volume moderate.
Speaker and Headphone Testing Guide
Use this frequency generator to evaluate your audio equipment. Here's how to test different aspects:
Frequency Response Test
Use the frequency sweep (20 Hz - 20 kHz) to identify any frequencies where your speakers are weak or strong. Listen for:
- Bass extension: How low can your speakers go? Many small speakers roll off below 80-100 Hz.
- Midrange clarity: The 1-4 kHz range should be clear and present.
- High frequency response: Listen for smooth treble without harshness.
- Resonances: Any frequencies that sound unnaturally loud indicate cabinet or driver resonances.
Stereo Balance Test
Test left and right channels separately to verify:
- Both channels are working
- Volume is balanced between left and right
- No cross-talk between channels
Polarity/Phase Test
Incorrect speaker wiring causes "out of phase" sound. Symptoms include:
- Weak or missing bass
- Sound seems to come from behind you
- Hollow, thin sound quality
- Poor stereo imaging
Audio Calibration Procedures
For professional audio work, calibration ensures accurate monitoring. Common procedures include:
- Reference Level Calibration: Use 1 kHz tone at -20 dBFS (digital) to calibrate monitor SPL. Professional studios often target 85 dB SPL at the listening position.
- Subwoofer Integration: Use 80 Hz tone to set crossover point and level-match your subwoofer to main speakers.
- Room Mode Identification: Sweep through 20-200 Hz to identify standing waves caused by room dimensions.
- Phase Alignment: Use polarity test to ensure all speakers are wired correctly and in phase.
Understanding Tinnitus
Tinnitus is the perception of sound when no external sound is present. It's commonly described as ringing, buzzing, hissing, or humming. While not a disease itself, tinnitus is often a symptom of underlying conditions like hearing loss, ear injury, or circulatory issues.
About Tinnitus Frequencies
Most tinnitus occurs in the 2,000-8,000 Hz range, often correlating with frequencies where hearing loss has occurred. Matching your tinnitus frequency can help with:
- Selecting effective masking sounds
- Notched sound therapy programs
- Communicating with audiologists
Important Caveats
Self-matching tinnitus frequency has limitations:
- Octave confusion is common (matching 2x or 0.5x the actual frequency)
- Tinnitus may have multiple frequencies or be broadband
- Professional audiometric testing is more accurate
- Always consult a healthcare provider about tinnitus
Standard Reference Frequencies
- 440 Hz (A4): The international standard for concert pitch since 1955. Most instruments and orchestras tune to this reference.
- 432 Hz: Alternative tuning sometimes called "Verdi pitch." Some claim it sounds more natural, though scientific evidence is limited.
- 1000 Hz: Common reference frequency for audio testing and calibration due to its position in the sensitive mid-range.
- Audiometric Frequencies: Hearing tests typically use 125, 250, 500, 1000, 2000, 4000, and 8000 Hz to assess hearing across the audible spectrum.
Frequency Sweeps
A frequency sweep (or tone sweep) continuously varies frequency over time. There are two main types:
- Linear Sweep: Frequency changes at a constant rate (Hz per second). Good for measuring frequency response but spends more time in higher octaves.
- Logarithmic Sweep: Frequency changes exponentially, spending equal time in each octave. Better matches human hearing perception and is preferred for room acoustics measurements.
Understanding Noise Types
Different types of noise have different frequency characteristics and applications:
White Noise
Equal energy at all frequencies. Sounds "bright" or "hissy" because higher frequencies are perceived as louder. Used for:
- Testing audio equipment
- Sleep masking
- Audio signal processing
Pink Noise
Equal energy per octave (falls off at 3 dB per octave). Sounds more balanced to human ears. Preferred for:
- Speaker testing and calibration
- Room acoustics measurement
- Reference for mixing
Brown Noise
Falls off at 6 dB per octave, emphasizing low frequencies. Sounds deeper and more "rumbling." Used for:
- Relaxation and focus
- Masking low-frequency sounds
- Sleep improvement
Safe Listening Practices
When using a frequency generator, follow these guidelines to protect your hearing:
- Start at Low Volume: Always begin with the volume low and gradually increase to a comfortable level
- Limit Exposure: Extended exposure to any sound above 85 dB can cause hearing damage
- Take Breaks: If testing for extended periods, give your ears regular rest
- Be Careful with High Frequencies: High-frequency tones can be perceived as louder and may cause discomfort
- Be Careful with Low Frequencies: Very low frequencies at high volume can damage speakers and potentially cause disorientation
- Avoid Sudden Changes: Abrupt volume or frequency changes can be startling and potentially harmful