The frequency of a sound tells us the number of vibrations per second in a sound wave. Frequency is measured in units called hertz (Hz). 1 Hz = 1 vibration per second.
High frequencies are measured in kilohertz (kHz)
1kHz = 1000 Hz = 1000 vibrations per second.
The range of human hearing is from 20 Hz to 20000 Hz.
1. What is 20 000 Hz in Khz ? 20Khz
2. Could a person with normal hearing hear a sound of 45 kHz? No, it could't.
3. What is the highest audible frequency when a person is 60 years old? 14 kHz
4. At what age does the range of hearing start to decrease? 20 years old
5. Could a person aged 40 hear a sound of frequency 15 kHz? yes, he could, because the maximum frequency that he can hear is 17 kHz.
6. Are there frequencies which mice can hear but humans cannot? yes there are, larger than 20kHz, but less than 70 kHz.
7. Which frequencies can humans hear but mice cannot? between 20 to 1000 Hz.
8. The signal generator is on the right side while the speaker on the left side.
9. Some students have their hands up while others have put their hands down. What conclusion can you draw from this observation? Some students have different range of hearing, hearing problems, or lying.
10. The teacher suspects that some students are not giving honest responses; they are keeping their hands up even when they can no longer hear the sound. How could he check if he is right? By increasing the frequency of signal generator more than 20Khz.