Sense of the Ear
• Hearing is our reception of the energy carried by sound waves
• Generated by the vibrations of molecules in a medium (there is no sound in a vacuum)
• These vibrations represent rapid alternations in pressure during compression and decompression of molecules
• Sound gives rise to periodic variations in air pressure
• The higher the frequency (i.e. The lower the wavelength), the higher the pitch of the sound. Unit = hertz (Hz)
• A normal human can hear sounds ranging between 20 and 12-20,000 Hz (depending on age)
• Most sensitive area: 1,000-3,000 Hz
• The greater the amplitude of the wave, the louder the sound. Unit = decibel (dB)
• Logarithmic scale - each 10dB increase represents a 10-fold increases in loudness (deci=1.10)
• Normal conversation ~ 60dB
• Levels above 80dB can lead to receptor damage (average level at a rock concert is 120dB, 10,000 times greater)
• Harmonic frequencies (overtones) are secondary vibrations in relation to the fundamental frequency
• Harmonic frequencies vary with the way the sound has been produced, this is why different instruments have a
different sounds (in music, this is known as timbre)
Integration of Physiological Systems Page 1
• Hearing is our reception of the energy carried by sound waves
• Generated by the vibrations of molecules in a medium (there is no sound in a vacuum)
• These vibrations represent rapid alternations in pressure during compression and decompression of molecules
• Sound gives rise to periodic variations in air pressure
• The higher the frequency (i.e. The lower the wavelength), the higher the pitch of the sound. Unit = hertz (Hz)
• A normal human can hear sounds ranging between 20 and 12-20,000 Hz (depending on age)
• Most sensitive area: 1,000-3,000 Hz
• The greater the amplitude of the wave, the louder the sound. Unit = decibel (dB)
• Logarithmic scale - each 10dB increase represents a 10-fold increases in loudness (deci=1.10)
• Normal conversation ~ 60dB
• Levels above 80dB can lead to receptor damage (average level at a rock concert is 120dB, 10,000 times greater)
• Harmonic frequencies (overtones) are secondary vibrations in relation to the fundamental frequency
• Harmonic frequencies vary with the way the sound has been produced, this is why different instruments have a
different sounds (in music, this is known as timbre)
Integration of Physiological Systems Page 1
