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2.3 Loudness and pitch

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2.3 Loudness and pitch

Summary: If you play a note of exactly the right pitch, even if it is not very loud, then you can break a glass. What is the difference between loudness and pitch? Tags: science oxford-science student-book-7 physics Created: 2026-05-19 Last Updated: 2026-05-19

After this topic, you will be able to:

  • describe the link between loudness and amplitude of Sound waves
  • describe the link between frequency and pitch of sound waves.

Think back

  1. What is the frequency of a sound wave?
  2. What is the amplitude of a sound wave?
  3. What is the pitch of a sound related to?

Key idea Loud sounds have a larger amplitude than soft sounds. High-pitched sounds have a higher frequency than low-pitched sounds.

Key words microphone, oscilloscope, loudness, decibel (dB), pitch, hertz (Hz), kilohertz (kHz)

If you play a note of exactly the right pitch, even if it is not very loud, then you can break a glass. What is the difference between loudness and pitch?

Seeing sound

You can attach a microphone to an oscilloscope, like the one in Figure 1, to see what the sound of your voice looks like. The microphone produces an electrical signal that represents the sound wave. The wave that appears on the screen is transverse. However, the sound waves you make when you talk are longitudinal.

An oscilloscope. It is a large rectangular box with a screen showing a wave. There are various buttons and knobs to control the oscilloscope.

Figure 1An oscilloscope shows you what a sound looks like as a wave.

What affects the loudness of a sound?

If a drummer hits a drum harder, the sound is louder.

You can bang a drum harder or hit a xylophone harder with a mallet to produce a louder sound. A loud sound has a larger amplitude than a soft sound. It also transfers more Energy. To make a louder sound, you need to make the amplitude bigger.

Figure 2 Explain why the drawings of waves in Figure 2 do not show what a sound wave is actually like. A drummer with drumsticks sitting in front of a drum set. There are two wave diagrams labelled as soft and loud. Figure 2You can see on an oscilloscope that a loud sound has a larger amplitude than a soft sound. Full text alternative to the content

How do you measure loudness?

Sounds made by volcanic eruptions are so loud that they can be heard thousands of miles away. Sound intensity determines loudness and is measured in decibels (dB). The decibel scale shown in Table 1 is not like a ruler. Each increase of 10 dB increases the intensity of sound by ten times. Table 1 Examples of sounds and their loudness in decibels. 0 dB

20 dB

40 dB

60 dB

80 dB

100 dB

120 dB

140 dB

cannot be heard

leaves rustling

talking quietly

normal speech

heavy traffic

jet engine

causes pain

gunshot

A 40 dB sound is 100 times more intense than a 20 dB sound. The volcanic eruption of Krakatoa in 1883 produced a sound of 180 dB.

B Use the data in Table 1 to suggest the loudness of a person shouting.

Working scientifically Two companies make ear defenders to protect people from loud noises. Plan an experiment to find out which pair is better at reducing sound intensity (loudness).

What affects the pitch of a sound?

Some singers can produce higher-pitched notes than others. The pitch of a note depends on the frequency of the sound wave. High-pitched sounds have a high frequency and low-pitched sounds have a low frequency. Frequency is measured in hertz (Hz) or kilohertz (kHz), and 1000 Hz = 1 kHz.

To make a higher-pitched sound, you need to make something vibrate faster. Faster vibration means there are more waves per second. You can see the difference in frequency between a high-pitched and a low-pitched sound in Figure 3.

Two people outdoors, with one blowing into a whistle. There are two wave diagrams labelled as low and high.

Figure 3A high sound has a higher frequency than a low sound. A whistle produces a sound with a high frequency. Full text alternative to the content

You can have a loud, high-pitched sound or a loud, low-pitched sound. Changing the frequency of a wave, such as sound, does not affect its amplitude.

C Describe what happens to the wavelength of a wave as its frequency increases.

Summary questions

  1. Copy and complete the sentences. The loudness of a sound depends on the amplitude/frequency of the sound wave. The pitch of a sound depends on the amplitude/frequency of the sound wave. Frequency is measured in decibels/hertz. Loudness is measured in decibels/hertz.
  2. A singer produces a soft, low note. Describe what their vocal chords would do to produce: a higher notea louder note.
  3. Compare the sound intensity of the volcanic eruption of Krakatoa with the sound intensity of a gunshot.

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