If you’ve ever heard a dog whistle you’ll know it doesn't work because it’s loud, it works because it’s a high pitched.
If we play a tone, at exactly the right frequency (pitch) then we can shatter glass.
We can see sound, using an oscilloscope. An oscilloscope shows the wave as a Transverse wave, however when you speak you are actually making a longitudinal wave.
You can see from the animation to the left, that although the amplitude changes, the frequency does not.
The greater amplitude means the louder the sound is.
To make a sound louder you need to transfer more energy. The louder something is, the bigger the vibration is.
Increasing the Pitch of something, means increasing the frequency. Notice the animation to the left.
The amplitude doesn't change, however the frequency of oscillations does.
We can measure frequency in Hertz (Hz) or Kilohertz (kHz). The higher the Hertz, the higher the pitch.
1kHz = 1000Hz.
To increase the frequency, we need to make something vibrate faster.
We can see this in our vocal cords. When we make a deep sound, our vocal cords vibrate slowly and far apart, while when we make a high pitch sound, the vocal cords vibrate quickly and close together.
As humans, our audible range is quite small, compared to other animals. Peoples audible range is roughly 20 to 20,000 Hz. Dogs audible range is 40 Hz to 60,000 Hz.
This is why dog whistles don’t affect us, but affect dogs.
Anything below 20 Hz is called infrasound, while frequencies above 20,000 Hz are called ultrasound.
Bats have an audible range of 2000 -
Whales have an audible range of 1000 -
Short Answer Question
1. Explain the link between Loudness and amplitude
2. How does frequency effect pitch.
3. Draw an example of a loud sound compared to a quiet sound, if you were to see it on a oscilloscope
4. Copy and select the correct words
The loudness of a sound depends on the amplitude/frequency and the pitch of the sound depends on the amplitude/frequency. Frequency is measured in hertz/meters. The range of frequencies you can hear is called the audible/visible range.
5. As a singer sings, they are capable of producing, not only, high and low pitch sounds, but also loud and soft sounds. Explain how this happens. (6 marks)
Don’t forget to write down the questions you got wrong in full!