Sound

Q1) What is the unit used to measure loudness.

Ans: Decibel (db )

Q2) what does the frequency of sound wave decide ?

Ans: pitch

Q3) what decides the loudness of sound wave ?

Ans: amplitude

Q4) if three different waves are in simple mathematical ratios, what kind of sound will they produce.

Ans: Musical or pleasant sound.

Q5) will sound wave having frequencies of 144Hz and 240 HZ produce a musical sound?

Ans: No, because they are not in mathematical ratio.

Q6) when does an object produce sound?

Ans: when it vibrates.

Q7) what is the frequency of a sound wave?

Ans: Frequency is the total number of oscillations made in one second.

Q8) what kind of sound waves produce a pleasant sound?

Ans: Musical notes

Q9) what is an echo ?

Ans: An echo is the reflected sound which is heard after sometime.

Q10) How do bats fly safely in darkness?

Ans: Echo-location helps bats to locate objects in darkness and fly safely at night.

Q11) what are wind instruments?

Ans: Wind instruments produce sound by a vibrating column of air.

Q12) what causes sound pollution?

Ans: Sounds that are loud, annoying or harmful to the human ear contribute to sound pollution.

Q13) How does sound travel?

Ans: When an object vibrates, the particles that surround it are set into vibration. The vibrating particles of air push the other air particles adjacent to them. This process continues and gives rise to a sound wave. Sound travels through a sound wave.

Q14) Explain amplitude of sound with a diagram?

Ans: Amplitude is the maximum distance travelled by an oscillating particles towards any one side from its initial position. It could be a distance from B to C or B to A.

Q15) Differentiate between audible and inaudible sound?

Ans: Audible sound is the sound that every animal is able to hear sounds in a certain range of frequency. There is an upper and lower limit of frequencies that each animal can hear. The human ears can hear sounds between 20 HZ and 20000 HZ.

Inaudible sound is the sound that lies outside this range and is not heard by human beings.

Q16) How is sound produced in humans

Ans: Human beings have an organ called larynx or the voice box which is involved in the production of sound. It is situated at the upper end of the windpipe in the neck. Stretched across the voice box are thin membranes called the vocal cords, when air is forced through these cords, they vibrate to produce sound.

Q17) Name two percussion instruments. How is sound produced in such instruments?

Ans: Percussion instruments: the drum and Tabla are percussion instruments. They produce sound by vibrating the membrane with the finger or palm.

Q18)How does the ear help us hear sound?

Ans: sound travels from its source to your ears. On reaching the ear, the sound wave vibrate the eardrum, the delicate membrane inside the ear. The vibration are picked up by special types of cells in the inner ear. These cells are attached to nerve fibres which transmit the vibrations to the brain, the brain process the information and helps you to recognise the sound.

Q19)Write short notes on:

a) Noise and musical sounds

Ans: the quality of sound depends on the different frequencies in the sound wave. A musical note is produced by a combination of frequencies which are in a simple mathematical ratio of whole numbers with each other.

All objects do not produce pleasant sounds. This is because they vibrate at a set of frequencies which are not simple mathematical ratios. Such vibrations produce noise. When a metal plate is dropped on the floor it produces noise.

b) ill effects of noise.

Noise pollution can affect our health and behaviour. Constant exposure to noise can make a person ill-tempered and restless. A person exposed to noise over a long period can develop high blood pressure and heart problems. Excessive noise disturbs sleep and leads to lack and concentration cause headache and earache.

Q20)Study the given illustration to explain why sound becomes taint as you move away from the source of sound.

Ans: sound becomes taint as you move away from the source of sound because as the sound moves progress, its particles lose energy while trying to vibrate the adjacent particles . as a result the amplitude of the vibrating particles decreases as the sound move further and so on. It becomes weaker and ultimately fades out. The distance covered by a sound wave depends on the loudness amplitude.