Edexcel iGCSE Physics -3.24P Human Hearing Range- Study Notes- New Syllabus

Frequency Range of Human Hearing

Frequency is the number of vibrations (or waves) produced each second and is measured in hertz (Hz).

The human ear can detect sound waves only within a limited frequency range.

Human Hearing Range

• The frequency range of human hearing is:

20 Hz to 20 000 Hz

• Sounds below 20 Hz are called infrasound.
• Sounds above 20 000 Hz are called ultrasound.
• These sounds cannot be heard by humans.

Audible, Infrasonic and Ultrasonic Sounds

• Infrasound (< 20 Hz): produced by earthquakes and large animals.
• Audible sound (20–20 000 Hz): human speech and music.
• Ultrasound (> 20 000 Hz): bats, dolphins, medical imaging.

Important Notes

• High-frequency sounds have a higher pitch.
• Low-frequency sounds have a lower pitch.
• The upper limit of hearing decreases with age.

Relevant Wave Relationship

Sound waves obey:

\( \mathrm{v = f\lambda} \)

• If frequency increases, wavelength decreases (for constant speed).
• This applies to all sound waves, audible or not.

Key Idea

• Humans can only hear a limited range of frequencies.
• Not all sound waves are audible.
• Frequency determines pitch, not loudness.

Important Points to Remember

• Hearing range is 20–20 000 Hz.
• Ultrasound and infrasound are outside human hearing.
• Animals may hear frequencies humans cannot.