SSC CGL 2025 Tier-I · 23 September 2025, Shift 3 · General Awareness · Question 15 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 13 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

What is the audible frequency range for the human ear?

(a)0–10000 Hz
(b)20–20,000 Hz
(c)2 kHz–20 kHz
(d)100–1000 Hz

Answer

Why

Correct — B. The human ear hears sound from about 20 Hz to 20,000 Hz, that is 20 Hz to 20 kHz.

Below 20 Hz lies infrasound and above 20 kHz lies ultrasound. Neither is audible to us.

The band 20–20,000 Hz is the one that matches both limits → option (b).

Why the others are wrong

(a)
0–10000 Hz — The range does not start at 0 Hz. Frequencies below 20 Hz are infrasound, which we cannot hear. The 10,000 Hz ceiling also drops the audible band from 10 to 20 kHz.
(c)
2 kHz–20 kHz — The lower limit is 20 Hz, not 2 kHz. This range wrongly leaves out the whole band from 20 Hz to 2,000 Hz, all of which the ear hears.
(d)
100–1000 Hz — 100–1000 Hz is far too narrow. It leaves out the audible band from 20 to 100 Hz and everything from 1 kHz up to 20 kHz.

Concept

Audibility depends on frequency. A sound wave is heard only if its frequency falls within the ear's range, about 20 Hz to 20,000 Hz for humans.

Waves below 20 Hz are infrasonic and waves above 20 kHz are ultrasonic. Both are real sound waves, just outside what the human ear detects.

Some animals hear beyond these limits. Dogs, for example, can hear sounds above 20 kHz.

The stem wants the textbook range. The exact limits vary from person to person, and the upper limit falls with age, but 20 Hz to 20 kHz is the standard figure.

Key facts

Human audible range: about 20 Hz to 20,000 Hz.
Infrasound: frequencies below 20 Hz.
Ultrasound: frequencies above 20 kHz, produced by animals such as bats and dolphins.
The upper limit of human hearing falls with age.

Study next

Infrasound and ultrasound, and the animals that use themThe wave equation v = fλUses of ultrasound: SONAR and medical imaging

Common traps

Picking 2 kHz–20 kHz because its upper figure matches. Both limits must be right, and the lower one is 20 Hz.
Mixing up the prefixes. Infra- means below the audible range, ultra- means above it.

Here the audible range is asked as straight recall among four numeric bands. A related frequency question, wavelength from v = fλ (340 ÷ 680 = 0.5 m), is at 16 Sep 2025, 16:00, GA Q.18.

Related PYQs

No directly related past PYQ was found.

Topic: Scientific Research — all 220 SSC CGL questions on it, every solved shift.