What is Hertz (Hz)?
A Hertz (Hz) is the scientific unit used to measure frequency.
- 1 Hertz = 1 complete sound wave (cycle) per second
Frequency determines the pitch of a sound.
- Low frequency = Low pitch
- High frequency = High pitch
Examples
| Frequency | Example Sound | Pitch |
|---|---|---|
| 20 Hz | Thunder, earthquake rumble | Very low |
| 60 Hz | Electrical hum | Low |
| 100 Hz | Bass guitar | Low |
| 440 Hz | Musical note A (concert pitch) | Medium |
| 1,000 Hz | Human speech | Medium |
| 5,000 Hz | Birdsong | High |
| 15,000 Hz | Dog whistle | Very high |
| 20,000 Hz | Highest sound most young people can hear | Extremely high |
Human Hearing Range
A healthy young person can generally hear sounds between:
20 Hz and 20,000 Hz (20 kHz)
This range changes throughout life.
Frequency Ranges
| Frequency Range | Common Sounds |
|---|---|
| 20–250 Hz | Thunder, bass guitar, kick drum |
| 250–2,000 Hz | Most speech, piano, guitar |
| 2,000–4,000 Hz | Consonants in speech (such as s, f, and t); this is where human hearing is most sensitive |
| 4,000–20,000 Hz | Birds, whistles, cymbals, high musical notes |
Why Are Humans Most Sensitive Between 2,000 and 4,000 Hz?
The human ear is especially sensitive to frequencies between 2,000 Hz and 4,000 Hz because many of the sounds that make speech understandable fall within this range.
These frequencies include important consonants such as:
- S
- T
- F
- Sh
Damage to hearing in this range can make speech sound muffled, even if louder sounds are still heard.
How Hearing Changes with Age
As we age, tiny sensory receptor cells called hair cells in the cochlea gradually become damaged or die.
Unlike many other cells in the body, human cochlear hair cells do not regenerate, so hearing loss is usually permanent.
The loss of high-frequency hearing with age is called presbycusis.
Typical Hearing Limits
| Age | Highest Frequency Usually Heard* |
|---|---|
| Teenagers and young adults | Up to about 20,000 Hz |
| Around 40 years | About 15,000–17,000 Hz |
| Around 50 years | About 12,000–14,000 Hz |
| Older adults | May hear only up to 8,000–12,000 Hz |
*These are typical averages. Individual hearing varies depending on genetics, health, medications, and noise exposure.
What Causes Age-Related Hearing Loss?
Several factors contribute to presbycusis, including:
- Natural aging of cochlear hair cells
- Years of exposure to loud sounds
- Changes in blood supply to the inner ear
- Genetics
- Certain medications that can damage hearing (called ototoxic medications)
Because the hair cells that detect the highest frequencies are located near the base of the cochlea, they are often the first to be damaged.
Noise-Induced Hearing Loss
Loud sounds can also permanently damage hair cells.
Examples include:
- Loud concerts
- Power tools
- Firearms
- Heavy machinery
- Listening to music at high volume through headphones or earbuds for long periods
Since hair cells do not regenerate, protecting your hearing is important.
Ways to Protect Your Hearing
- Keep headphone volume below about 60% of maximum when possible.
- Wear hearing protection in noisy environments.
- Take regular listening breaks.
- Limit the amount of time spent around loud sounds.
Frequency vs. Loudness
People often confuse frequency and loudness, but they measure different properties of sound.
| Measurement | Unit | What It Measures |
|---|---|---|
| Frequency | Hertz (Hz) | How high or low a sound is (pitch) |
| Loudness (Sound Intensity) | Decibels (dB) | How loud or soft a sound is |
For example:
- A 100 Hz bass note and a 5,000 Hz bird chirp can be played at the same loudness (dB), even though they have very different pitches (Hz).
Key Terms
- Hertz (Hz): One cycle of a sound wave per second; measures frequency.
- Frequency: The number of sound wave cycles per second; determines pitch.
- Pitch: How high or low a sound is perceived to be.
- Decibel (dB): A unit used to measure sound intensity or loudness.
- Hair cells: Sensory receptor cells in the cochlea that convert sound vibrations into electrical signals.
- Cochlea: A spiral-shaped, fluid-filled structure in the inner ear responsible for hearing.
- Presbycusis: Age-related hearing loss, particularly affecting high-frequency sounds.
- Noise-induced hearing loss: Permanent hearing damage caused by prolonged or intense exposure to loud sounds.
Psychology Exam Tip
Remember this simple rule:
- Hertz (Hz) = Pitch (high or low sound)
- Decibels (dB) = Loudness (soft or loud sound)
Keeping these two units separate will help you answer questions about hearing accurately.
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