Chapter 2 - Sound Flashcards
Define pitch.
A characteristic through which we differentiate between shrill and grave sounds. It is not a physical characteristic, so it cannot be measured directly. It is essentially the perception of frequency and depends upon the wavelength and speed of sound.
Pitch describes the number of vibrations produced by vocal chords in unit interval of time (1 sec). This is why it is related to frequency: it is proportional to it.
Low pitch waves mean less frequency while higher means vice versa.
Define “loudness”
Not a physical quantity, measured instead on the basis of amplitude. Which means that it tests the strongest levels of aound waves, and is studied in decibel.
Loudness is proportional to (amplitude)^2
It can also be described at being dependent upon the energy received by the ears in unit time interval.
What 4 factors effect the loudness of sound?
Vibrational amplitude, surface area of the source of sounds (to which it is proportional to aka more SE = More sound), Distance from the source of sound and the sensitivity of the ears of the listener.
What is timbre?
It helps us differentiate between the quality of sound waves with the same pitch and loudness. It helps us study dynamic characteristics as well as harmonic contacts of sounds. The quality of sound depends on relative overtones, which means a harmonic frequency greater than the frequency of the sound.
What is harmonic contact?
Harmonic contact” typically refers to the point of physical contact between two components in a mechanical system, which means that during the motion of sound waves, the pathway of kinetic transmission is followed by the molecules of the medium for transmitting energy.
What is meant by the intensity of sound wave?
Energy transmitted by sound wave per unit perpendicular area per unit time. Represented by “I”.
Energy transmitted / Area × time = E /A × 1 = P / A
In other words, the intensity of sound wave is the power delivered by the sound wave per unit perpendicular are. Its units are watt / metre^2 (W/m^2)
What is the relation between amplitude and the intensity of sound waves?
Intensity is directly proportional to the square of the amplitude. This means that a small increase in amplitude of a sound wave can lead to a significant rise in sound intensity.
(Change in amplitude)^2 / 2 (density of medium) (speed of sound) = I = (A)^2 / 2pv
Factors of sound propagation that affect the speed of sound.
Temp: Increase in 1c of temp increases sound speed by 0.62 m/s.
Dynamic state of medium: If wind is blowing, sound will be fast as well.
Viscosity of medium: Speed does not depend on viscosity itself, but the term suggests resistance in viscous substances that tends to change the behaviour of molecules.
Characteristics of Noise.
Non-rhythmic
graphical waveform shows variable
energy states.
Wave form in the graphs of noise suggest multiple frequencies
Graphs shows irregular intensities of distribution.
What is an echo?
The bouncing back of sound due to a wave reflection phenomenon. It is a distinct sound with a separate wave from the original noise. The hardness of echoes is not very high, and it prolongs the sensation of the original sound.
By an echo, the distance of any object under water can be calculated by multiplying the speed of sound by the time taken by the echo.
Human ears can generally hear sound waves within 0.1 second, so the time interval gap between sound and echo is 0.1 second. The maximum distance required for the production of an echo is 1/20th times the value of the speed of sound. For example, if the sound is 332 m/s for the production of echo, its distance would be 16.6m
mathematically S= v t / 2
How is the speed of sound related to temp?
Heat, like sound, is a form of kinetic energy. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly. Speed of sound at any temperature is given by 331 + 0.6T
Why do spectators hear the sound of impact after the ball is hit by a batsman playing cricket in a stadium?
Because sound travels at a rate of 340 ms^-1 in the air, which is why it is heard as delayed.
Nature of soundwaves.
Mechanical and longitudinal in nature, also called pressure waves. produced by vibrations propagated by molecules within a medium. This vibration is converted into a chain propagation along a pathway till the sound has travelled across a distance.
Compression is that high pressure portion within a wave where molecules of a medium acquire low viscosity produced due to vibrational kinetic energy originated at the sound’s source. Here, molecules have very short distances between them.
Rarefaction is that low pressure portion within a sound wave where molecules of a acquire high velocity.
Types of sound waves?
All sound waves are dependent on references, for example, the difference between loud and hushed, soft or hard noises, or shrill or grave sounds. Based on this, they are generally categorzed into rhytmic or non rhythmic sound waves.
Rhythmic sound waves are pleasant with consistent frequencies that are like music. Non rhythmic sound waves are irregular, and unpleasant like construction noise.
Human ears can listen to sound with the ranges of 20 to 20,000 Hertz. Sounds above this threshold are called ultrasonic, while sounds below this threshold are infrasonic.
What are some turns for soundwaves?
Wavelength: The distance between consecutive crests and troughs is called the wavelength of the sound wave. Its symbol is the Greek letter lambda (λ), and its SI unit is meter.
Amplitude is the maximum displacement of a trough or crest about the wave’s center. It tells us about the energy level carried by sound waves, and is measure in meters.
Frequency the occurrence of a number of waves in a set unit of time.
Represented as f and has the unit hertz. One heartz means one sound wave per second.
Time period; required to create or propagate one sound wave. SI unit is seconds and is represented by T.
What is noise?
It is a generally unpleasant sound. sound waves an be studied in two different categories, periodic and non periodic. Human ears are built only for periodic sound waves, which are pleasant like music, while non-periodic sound waves are irritating and unpleasant.
The range of periodic sound waves is around 15 to 4000 hertz, beyond which periodic sound waves become non-periodic waves.
How much intensity level increases when intensity of louder sounds is double the intensity of the fainter sound
Intensity of first sound I1=i
Intensity of second sound 12=2I
Intensity level is given by 10log I2/I1.
putting in the relevant values,
10log 2I/I1 = 10 log 2
10 . 3.3010 =3 db.
Hence, sound will increase by 3db.
What is the speed of sound at 15 C in air if the speed of sound is 332 ms ar 0 C.
speed of sound in 0 C = V0 = 332
speed of sound in the air= T = 15 C = V=?
speed of sound is given by 332 + 0.6 T
332 + 0.6 . 15
332 + 9
341
