Properties of Sound

EQ: How does intensity, loudness, frequency and pitch affect sound

waves?

Vocabulary

• Intensity – the amount of energy an sound wave carries per second through a unit area. Measured in watts per meter squared. W/m²– Example – When a sound wave carries a

large amount of energy, the molecules of the medium move a greater distance as the wave pass by, and the sound has a greater amplitude EQ: How does intensity, loudness,

frequency and pitch affect sound waves?

Vocabulary

• Loudness – sound level, describes what you actually hear. A sound wave of greater intensity sounds louder

• Decibels (dB) – measures loudness. A sound you can barely hear is 0 dB. 100dB can damage your ears.

EQ: How does intensity, loudness, frequency and pitch affect sound waves?

Intensity determines loudness.

SECTIONOUTLINESECTIONOUTLINE

A sound wave with a higher amplitude and energy is perceived as a louder sound.

EQ: How does intensity, loudness, frequency and pitch affect sound waves?

Intensity determines loudness.

A sound wave with a lower amplitude and energy is perceived as a softer sound.

EQ: How does intensity, loudness, frequency and pitch affect sound

waves?

Vocabulary

Frequency – the number of vibrations that occur per second in a sound wave. Measured in Hertz. A frequency of 50Hz means 50 vibrations per second.– We hear sounds with frequencies that are between

20Hz and 20,000Hz

Ultrasound – sound waves with frequencies above the normal range of hearing

Infrasound – sound waves with frequencies below the human range of hearing EQ: How does intensity,

loudness, frequency and pitch affect sound waves?

Vocabulary

• Pitch – a description of how high or how low a sound seems to a person.

• Pitch depends on the frequency of a sound wave– High frequency means high pitch– Low frequency means low pitch

EQ: How does intensity, loudness, frequency and pitch affect sound waves?

Frequency determines pitch.

A sound wave with a higher frequency and shorter wavelength is perceived to have a higher pitch.

A sound wave with a lower frequency and longer wavelength is perceived to have a lower pitch.

EQ: How does intensity, loudness,

frequency and pitch affect

sound waves?

Piano Example of Pitch

Tension - A tighter string produces a higher frequency. Therefore you hear the sound at a higher pitch.

Length of the string - right side of the piano has higher pitch, shorter string. Left side of piano has lower pitch, longer string

Thickness of a string – thicker means lower pitch EQ: How does intensity, loudness, frequency and

pitch affect sound waves?

Vocabulary

• Resonance – when the frequency of the sound wave exactly matches the frequency of an object

EQ: How does intensity, loudness, frequency and pitch affect sound waves?

Doppler Effect

The apparent change in frequency as a wave source moves in relation to the listener

EQ: How does intensity, loudness,

frequency and pitch affect

sound waves?

Doppler Effect

• As a sound source moves toward the listener, the waves reach the listener with a higher frequency. The pitch appears to increase because of the Doppler effect

EQ: How does intensity, loudness, frequency and pitch

affect sound waves?

Class Work and Homework

Fill In• What did I learn• Confused• Say

• Read pages O 46 – O 51. • Questions 1-6, p. O 51• 2-2 Worksheet

EQ: How does intensity, loudness, frequency and pitch affect sound waves?