When the pitch of sound increases, which one of the following increases?
- (a)Intensity
- (b)Loudness
- (c)Wavelength
- (d)Frequency
Correct — D, Frequency. Pitch is the sensation that separates a shrill sound from a deep one, and the physical quantity behind it is frequency — the number of vibrations reaching the ear each second. Tighten a sitar string, shorten a flute's air column or spin a faster-vibrating tuning fork and the frequency rises, and the ear reports a higher pitch. Pitch and frequency move together, one being the perception of the other.
- (a)Intensity — Intensity is the sound energy crossing unit area per second, set by the wave's amplitude. It decides how strong the sound is, not how shrill — a whisper and a shout can share the same pitch.
- (b)Loudness — Loudness is the ear's perception of intensity and again tracks amplitude, not frequency. A bass drum can be deafeningly loud yet very low in pitch.
- (c)Wavelength — Wavelength moves the opposite way. The speed of sound is fixed in a given medium, so v = fλ means wavelength must SHRINK as frequency and pitch rise.
Three properties describe a musical sound and each has its own physical cause. Pitch follows frequency, loudness follows amplitude (through intensity), and quality or timbre follows the mixture of overtones a source produces. Keeping the three pairs separate is the whole content of this question, because the examiner offers two amplitude words and one wavelength word as bait.
Read the pairing off the wave equation v = fλ. In a given medium the speed v is a constant of the medium, so frequency and wavelength are locked in inverse proportion — raise the pitch and the wavelength necessarily falls, which is why option (c) is wrong in direction rather than in topic. Intensity and loudness both belong to the amplitude family, so they cannot be the answer to a pitch question at all. A useful physical anchor is the human voice, whose fundamental frequency averages about 125 Hz in adult men, about 210 Hz in adult women and over 300 Hz in children — shorter, thinner vocal folds vibrate faster and are heard as a higher pitch.
- Pitch is fixed by frequency; loudness by amplitude and intensity; quality or timbre by the pattern of overtones.
- Since v = fλ and the speed of sound is fixed in a given medium, higher pitch means shorter wavelength.
- The human audible range runs roughly from 20 Hz to 20 000 Hz; above that is ultrasound.
- Voice fundamental frequency averages about 125 Hz in adult men, about 210 Hz in adult women and over 300 Hz in children.
- Loudness is measured in decibels, a logarithmic scale, while frequency is measured in hertz.
Pitch belongs to the frequency column — option (d); intensity and loudness belong to amplitude.
- Treating loudness and pitch as the same idea.
- Saying wavelength rises with pitch — it falls, because v = fλ with v fixed.
- Assuming a higher-frequency sound must also be louder.
As a direct pitch-to-frequency match like this, as its mirror image asking what loudness depends on, or through the sitar-versus-flute framing that tests quality.
When the same note is played on a sitar and a flute, the sound produced can be distinguished from each other because of the difference in
- (a) pitch, loudness and quality
- (b) pitch and loudness
- (c) quality only
- (d) loudness only
Answer(c) quality only
The third member of the same trio. This NDA item pins pitch to frequency; the UPSC item isolates quality (timbre) by holding pitch and loudness identical between two instruments.
Consider the following statements: 1. A flute of smaller length gives waves of lower frequency. 2. Sound travels in rocks in the form of longitudinal elastic waves only. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer(d) Neither 1 nor 2
The same frequency-and-pitch link in an instrument. A shorter flute gives a HIGHER frequency and so a higher pitch, which is why statement 1 there is false.
The loudness of sound depends upon the
- (a) velocity of sound waves in the medium.
- (b) amplitude of the sound waves.
- (c) frequency of the sound waves.
- (d) frequency and velocity of the sound waves.
Answer(b) amplitude of the sound waves.
The exact mirror of this item, and the reason its distractors work. Pitch goes with frequency, loudness goes with amplitude — the NDA examiner has asked both halves of the pair.
- practice — not a real PYQ
The loudness of a sound is decided mainly by its
- (a)frequency
- (b)amplitude
- (c)wavelength
- (d)speed
Answer(b) amplitude — a larger amplitude carries more energy, which the ear reports as greater loudness.
- practice — not a real PYQ
As the frequency of a sound wave increases in the same medium, its wavelength
- (a)increases
- (b)decreases
- (c)remains unchanged
- (d)becomes zero
Answer(b) decreases — the speed is fixed by the medium, so v = fλ makes wavelength inversely proportional to frequency.