Characteristics of Sound

Pitch

Pitch

Pitch refers to the highness or lowness of a sound.

The pitch of a sound that you hear depends on the frequency of the sound wave.

Pitch and Frequency

• Sound waves with a high frequency have a high pitch and sound waves with a low frequency have a low pitch.

• High frequency means more vibrations hitting the ear.

• Pitch is how high or how low a sound seems to be.

• Healthy humans can hear from 20 Hz to 20,000 Hz

• We are most sensitive from 440 Hz to 7,000 Hz.

Changing Pitch

• Lungs: Air From the lungs rushes up the trachea• Vocal Cords: which are

located in your voice box, or larynx vibrate as air rushes pass them• Sound: Sound waves

produced by the vibrating vocal cords come out through the mouth

•A man’s vocal chords are normally longer and more massive than a female’s voice. Hence, a male’s voice is low pitched compared to the female’s voice.

Loudness

Loudness

The degree of loudness or faintness of a sound depends upon the different factors

1. Amount of energy of a sound

2. Distance from the source of sound

3. The state of the medium through which the sound is transmitted

4. The amount of the original vibrations

5. The frequency of the vibration

6. Area to which the sound is produced

Energy of a Sound Source

The greater the energy used to make a sound, the louder the sound

Example: Playing a guitarWhen you use more energy

to pull the strings of the guitar the louder the noise produced by the guitar is.

The more energy you use, the larger the amplitude

The larger the amplitude produces a louder sound.

Amplitude is the distance between the normal position to the final position of an object which is producing specific vibration.

Distance From a Sound SourceLoudness increases the closer you are to a sound source.– Close to the sound source, the sound waves cover a small

area– As waves travel away from the sound source, it covers more

area

The total energy of the wave stays the same whether it’s close to the source or far away from it– The closer the sound wave is to its source, the more energy

it has in a given area.

Distance From a Sound SourceThe amount of energy a sound wave carries per second through a unit area is its Intensity

A sound wave of greater intensity sounds louder

When you move away from the sound source, loudness decreases, because the intensity decreases.

Measuring Loudness

Loudness is measured using the unit called the Bel (B) in honor of Alexander Graham Bell. A bel is a rather large unit; the smaller unit is decibel (dB) is often used instead.

1B = 10dB

Intensity Levels of Common Sounds

Source of Sound Intensity level in dB

Intensity I (W/m2)

Threshold of hearing O 1 × 10-12

Rustle of Leaves 10 3.2 × 10-11

Whisper 20 1 × 10-10

Ordinary conversation 65 3.2 × 10-6

Busy street traffic 70 1 × 10-5

Auto interior moving at 90 kph 75 2.8 × 10-4

Loud indoor rock concert 100 1 × 10-2

Threshold of pain 120 1 × 101

Quality

QUALITY

•  Quality or timbre is that the property of tone that distinguishes it from another tone of the same pitch and intensity but produced by different sources (voices and instruments).• Timbre is then a general term for the distinguishable characteristics of a tone. 

• These difference in quality are due to the varying vibrations of the sound sources.  

 In simple terms, timbre is what makes a particular musical sound different from another, even when they have the same pitch and loudness. 

For instance, it is the difference between a guitar and a piano playing the same note at the same loudness.