Experiment 4 — Pitch, Loudness and the Bell Jar

Topic: Physics · Class 8 · Sound: vibration, frequency, amplitude and medium

Aim: Produce a high-pitched, loud sound that the microphone can hear (above 400 Hz).

Daily: A tabla tightened with its straps rises in pitch, a veena string pressed shorter sings higher, and a loudspeaker is simply a cone vibrating the air. In outer space, no alarm would ever be heard.

Question: An alarm clock rings inside a jar. You pump all the air out. What do you hear?

Exp: Sound needs a material medium. As the air is removed, there is nothing left to carry the vibration.

Question: The pitch of a sound is decided by its…

Exp: More vibrations per second means a higher pitch.

Exp: Bigger vibrations carry more energy.

Question: Sound travels fastest in…

Exp: Closely packed particles pass the vibration on quickly.

Question: The human hearing range is roughly…

Exp: Above this range is ultrasound.