Sound

• Sound waves are longitudinal waves that require a medium to travel through, such as air or water.
• Sound waves can be described by their frequency (number of oscillations per second) and amplitude (height of wave).
• The sound level meter is used to measure the intensity of sounds.
• In solids, sound waves can be transmitted along the length of the material without being absorbed.
• In liquids, sound waves can also be transmitted but with less energy loss than in gases.
• The human ear is sensitive to sound frequencies between about 20 Hz and 20 kHz.
• Loudness refers to how intense a sound seems, which depends on its amplitude.
• Pitch refers to the perceived highness or lowness of a sound, which depends on its frequency.
• Sound is produced by a vibrating body and travels in the medium from one place to another in the form of compressional waves.
• Loudness is a feature of sound by which a loud and a faint sound can be distinguished, and it depends upon the amplitude, surface area and distance from the vibrating body.
• The intensity of sound is the energy flowing per second through unit area held perpendicular to the direction of sound waves, and bel is the unit of the intensity.
• Pitch of the sound is the characteristics of sound by which a shrill sound can be distinguished from a grave one, and it depends upon the frequency.
• The quality of sound is the characteristics of sound by which two sound waves of same loudness and pitch are distinguished from each other.
• Noise pollution is a major issue of concern in some big cities, and any form of sound which disturbs the normal functioning of any natural ecosystem or some human community is the cause of noise pollution.
• Noise pollution can be reduced to acceptable level by replacing the rusty noisy machinery with environment friendly machinery and equipments, putting sound-reducing barriers, or using hearing protection devices.
• Acoustic protection is the technique or method used to absorb undesirable sound energy by soft and porous surfaces, and this can be done by using soft, rough and porous materials.
• Human audible frequency range lies between 20 Hz to 20, 000 Hz.
• Sound waves of frequency higher than 20, 000 Hz are called ultrasound while sound waves of frequency lower than 20 Hz are called infrasound.
• Ultrasound is used in many fields of science and technology such as medical, engineering, agriculture.
• In medical field ultrasound is used to diagnose and treat different ailments.
• Ultrasound is also used to locate underwater depths or for locating objects lying deep on the ocean floor, the technique is called SONAR, an acronym for sound navigation and ranging.
• Variation of loudness with amplitude

  A) Amplitude

  B) Amplitude

  C) Small Amplitude

  D) Large Amplitude

  E) Small Amplitude = Quiet Sound

  F) Large Amplitude = Large Sound

  
• Variation of pitch with frequency

  A) Low Frequency = Low Pitch

  B) High Frequency = High Pitch