TutorForAll

Science 7–10 · Year 9

Sound through solids, liquids and gases: string telephones, a bench and an underwater tap

Physical sciences — Waves and motion: waves, sound and light (NSW Stage 5 focus area)

PracticalLow risk

The idea

Sound travels through any material whose particles can pass on a vibration, and it travels faster and further through solids than through air.

What you need

  • paper cups, 4
  • string 10 m, fishing line 10 m and thin wire 10 m, 1 each
  • paperclips, 4
  • wooden metre rule or bench top
  • mechanical ticking timer or watch, 1
  • large bucket of water and two spoons, 1 set

How to do it

  1. Make a string telephone with two cups joined by 10 m of string. One learner whispers a sentence into a cup while the other listens; repeat with the string slack and then taut. Record what is heard.
  2. Replace the string with fishing line and then thin wire; repeat and rank the three for clarity.
  3. Place the ticking timer on the bench. Listen from 1 m in air, then rest an ear on the bench 1 m away; compare loudness.
  4. One learner scratches the far end of a metre rule very lightly while another listens with an ear on the near end, then with the ear 5 cm above the rule; compare.
  5. With the bucket on the floor, one learner kneels and presses an ear to the outside wall of the bucket while another taps two spoons together under the water; compare with the same tapping in air.
  6. Use the observations as evidence to argue whether sound needs air to travel.

What you should see

A taut string carries a whisper that cannot be heard through the air over the same 10 m; a slack string carries almost nothing. The ranking of string, fishing line and wire depends on how taut each is held. The tick heard through the bench is louder than through air at the same distance, and the light scratch is clear through the rule but almost inaudible through the air 5 cm above it. Tapping under water is heard clearly through the bucket wall. The learner knows it worked when the taut string carries speech that the air gap does not.

What changes

What you change
material carrying the sound (string, line, wire; air, wood, water)
What you measure
loudness and clarity heard (ranked, or measured with the phyphox Audio Amplitude reading)
What you keep the same
  • same source loudness
  • same distance
  • same listener

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • Sound needs air and cannot pass through solids or water.
  • Solids stop sound because they are solid.
  • Sound travels fastest in air because air is easy to move.

Safety card

Low riskLearners carry it out

Hazards

  • thin wire cutting fingers
  • water spills

Controls

  • handle wire by the paperclip ends
  • keep the bucket on the floor

Note

No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Sources

The pages the author read to write this activity.

  1. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/outcomes
  2. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/content/stage-5/faafd3c3df
  3. spark.iop.org/sounds-through-solids-and-liquids-well-gases
  4. spark.iop.org/talking-telephones
  5. www.iop.org/sites/default/files/2020-05/Teaching-sound-waves.pdf

All Concept Studio activities