AN ACTIVE LEARNING ASSIGNMENT IN “AUDIO AND VIDEO SYSTEMS” GUIDED BY : PROF. VISMAY YAGNIK PROF. NIRAV PATEL PREPARED BY : MOHNISH LAVANIA ( ) GUPTA MAHENDRA ( ) HETVI NAIK ( ) MOHIT SARDA ( ) ANKIT LAKHANI ( ) C. K. PITHAWALLA COLLEGE OF ENGINEERING AND TECHNOLOGY (009)

Characteristics of Sound

INTRODUCTION  In physics, sound is a longitudinal wave motion that produce compression and rare fraction in air.  It propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water (longitudinal wave).

CHARACTERISTICS OF SOUND  Sound waves have frequency; that is, the pitch of sounds goes up or down. The SI unit of frequency is called a Hertz, often written as Hz.  The amplitude of a sound determines its volume (loudness).  Tone is a measure of the quality of a sound wave.  Sound travels the fastest in solid, second in liquid, slowest in gas.  The speed of sound in air is 343.2m/s

Frequency is dependent on wavelength and the speed of sound. It is calculated with the following equation:

Pitch

Pitch refers to the highness or lowness of a sound. The pitch of a sound that you hear depends on the frequency of the sound wave.

Pitch and Frequency Sound waves with a high frequency have a high pitch and sound waves with a low frequency have a low pitch.

High frequency means more vibrations hitting the ear. Pitch is how high or how low a sound seems to be. Healthy humans can hear from 20 Hz to 20,000 Hz We are most sensitive from 440 Hz to 7,000 Hz.

Changing Pitch Lungs: Air From the lungs rushes up the trachea Vocal Cords: which are located in your voice box, or larynx vibrate as air rushes pass them Sound: Sound waves produced by the vibrating vocal cords come out through the mouth

A man’s vocal chords are normally longer and more massive than a female’s voice. Hence, a male’s voice is low pitched compared to the female’s voice.

Loudness

The degree of loudness or faintness of a sound depends upon the different factors 1.Amount of energy of a sound 2.Distance from the source of sound 3.The state of the medium through which the sound is transmitted 4.The amount of the original vibrations 5.The frequency of the vibration 6.Area to which the sound is produced

Energy of a Sound Source The greater the energy used to make a sound, the louder the sound Example: Playing a guitar When you use more energy to pull the strings of the guitar the louder the noise produced by the guitar is.

The more energy you use, the larger the amplitude The larger the amplitude produces a louder sound. Amplitude is the distance between the normal position to the final position of an object which is producing specific vibration.

Distance From a Sound Source Loudness increases the closer you are to a sound source. – Close to the sound source, the sound waves cover a small area – As waves travel away from the sound source, it covers more area The total energy of the wave stays the same whether it’s close to the source or far away from it – The closer the sound wave is to its source, the more energy it has in a given area.

Distance From a Sound Source The amount of energy a sound wave carries per second through a unit area is its Intensity A sound wave of greater intensity sounds louder When you move away from the sound source, loudness decreases, because the intensity decreases.

Measuring Loudness Loudness is measured using the unit called the Bel (B) in honor of Alexander Graham Bell. A bel is a rather large unit; the smaller unit is decibel (dB) is often used instead. 1B = 10dB

Intensity Levels of Common Sounds Source of SoundIntensity level in dB Intensity I (W/m2) Threshold of hearingO 1 × Rustle of Leaves × Whisper20 1 × Ordinary conversation × Busy street traffic70 1 × Auto interior moving at 90 kph × Loud indoor rock concert100 1 × Threshold of pain120 1 × 10 1

Quality

QUALITY Quality or timbre is that the property of tone that distinguishes it from another tone of the same pitch and intensity but produced by different sources (voices and instruments). Timbre is then a general term for the distinguishable characteristics of a tone.

These difference in quality are due to the varying vibrations of the sound sources.

In simple terms, timbre is what makes a particular musical sound different from another, even when they have the same pitch and loudness. For instance, it is the difference between a guitar and a piano playing the same note at the same loudness.

DOPPLER EFFECT  The Doppler Effect is the change in frequency of a wave for an observer moving relative to its source.  It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, Czech.  When the source of the waves is moving toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrivals of successive wave crests at the observer is reduced, causing an increase in the frequency.