Q1.
What if … humans could detect ultrasonic waves like dogs can? What would be the advantages and disadvantages?
Answer
We would gain a great deal of extra information about the world, but we would also be flooded with noise we currently do not notice at all.
| Advantages | Disadvantages |
|---|---|
| We could hear bats and dolphins hunting, and follow animal communication that is silent to us today. | Constant noise from ultrasonic pest repellers, some machinery, vehicle parking sensors and cleaning equipment. |
| A doctor or technician could hear a flaw in a metal block or a blocked pipe directly, without instruments. | Ultrasonic welding and industrial cleaning plants would become unbearable workplaces and would need heavy shielding. |
| Ultrasonic reversing sensors, security alarms and range finders could be checked by ear. | Higher-frequency sound is also higher-energy for the same amplitude, so long exposure could damage hearing faster. |
| Better echolocation of our own: short-wavelength sound reflects from small objects, so we could judge small obstacles in the dark. | Speech and music would be buried under a permanent hiss, making concentration and conversation harder. |
Why ultrasound is so useful for locating things: at 40 kHz in air, λ = 344 m s⁻¹ ÷ 40 000 s⁻¹ ≈ 0.0086 m, less than a centimetre. A wave reflects sharply only from objects that are not much smaller than its wavelength, so ultrasound bounces cleanly off small targets that ordinary sound would simply flow around. That is exactly why it can image a baby's organs, break a kidney stone, or find a crack inside a metal block.
Tip: when a question asks for advantages and disadvantages, give the physical reason for each side rather than a list of opinions. Here both sides come from the same fact — short wavelength and high energy.