GRADE 7 SCIENCE - PROPERTIES OF SOUND.ppt
- 1. Properties of Sound Properties of Sound ăWhat are the characteristics of sound What are the characteristics of sound waves? waves? ă sound wave: sound wave: a longitudinal wave that is caused by a longitudinal wave that is caused by vibrations and that travels through a material vibrations and that travels through a material medium medium ïź In air, sound waves spread out in all directions In air, sound waves spread out in all directions away from the source. away from the source.
- 2. Properties of Sound, Properties of Sound, continued continued ïź The speed of sound depends on the medium. The speed of sound depends on the medium. âą The speed of sound in a particular medium The speed of sound in a particular medium depends on how well the particles can transmit depends on how well the particles can transmit the motions of sound waves. the motions of sound waves. âą Sound waves travel faster through liquids and Sound waves travel faster through liquids and solids than through gases. solids than through gases.
- 3. Properties of Sound, Properties of Sound, continued continued Speed of Sound in Various Mediums Speed of Sound in Various Mediums
- 4. Speed of Sound Speed of Sound
- 5. Properties of Sound, Properties of Sound, continued continued ïź Pitch is determined by frequency. Pitch is determined by frequency. âą pitch: pitch: a measure of how high or low a sound is a measure of how high or low a sound is perceived to be, depending on the frequency of the perceived to be, depending on the frequency of the sound wave sound wave âą A high-pitched sound corresponds to a high frequency. A high-pitched sound corresponds to a high frequency. âą A low-pitched sound corresponds to a low frequency. A low-pitched sound corresponds to a low frequency.
- 6. Pitch Pitch
- 7. Properties of Sound, Properties of Sound, continued continued ïź Humans hear sound waves in a limited frequency Humans hear sound waves in a limited frequency range. range. ïź Any sound with a frequency below the range of Any sound with a frequency below the range of human hearing is known as an infrasound. human hearing is known as an infrasound. ïź Infrasonic frequency: Infrasonic frequency: vibrational frequencies below 20 Hz vibrational frequencies below 20 Hz ïź Any sound with a frequency above human hearing Any sound with a frequency above human hearing range is known as an ultrasound. range is known as an ultrasound. ïź Ultrasonic frequencies: Ultrasonic frequencies: vibrational frequencies beyond vibrational frequencies beyond 20 000 Hz. 20 000 Hz.
- 8. Comparing Infrasonic and Comparing Infrasonic and Ultrasonic Sounds Ultrasonic Sounds
- 9. Properties of Sound, Properties of Sound, continued continued ïź Loudness is determined by intensity. Loudness is determined by intensity. ïź loudness loudness: : depends partly on the energy contained in the sound wave. depends partly on the energy contained in the sound wave. It is a psychological sensation that differs for different people. It is a psychological sensation that differs for different people. ïź intensity: intensity: describes the rate at which a sound wave transmits energy describes the rate at which a sound wave transmits energy through a given area of a medium. It can be measured by various through a given area of a medium. It can be measured by various instruments like the instruments like the oscilloscope oscilloscope. . ïź Intensity depends on Intensity depends on âą the amplitude of the sound wave the amplitude of the sound wave âą your distance from the source your distance from the source ïź The greater the intensity of a sound, the louder the sound will seem. The greater the intensity of a sound, the louder the sound will seem. ïź Intensity is measured in units called Intensity is measured in units called decibels decibels, dB. , dB.
- 10. Properties of Sound, Properties of Sound, continued continued ïź The unit of intensity level for sound is decibel The unit of intensity level for sound is decibel (dB), which was named after (dB), which was named after Alexander Alexander Graham Bell Graham Bell who invented the telephone. who invented the telephone.
- 11. Sound Intensity and Decibel Sound Intensity and Decibel Level Level
- 12. ă How do ears help humans hear sound waves? How do ears help humans hear sound waves? ă The human ear is a sensitive organ that senses The human ear is a sensitive organ that senses vibrations in the air, amplifies them, and then vibrations in the air, amplifies them, and then transmits signals to the brain. transmits signals to the brain. ïź Vibrations pass through three regions in the ear. Vibrations pass through three regions in the ear. ïź Your ear is divided into three regionsâouter, middle, and Your ear is divided into three regionsâouter, middle, and inner. inner. Hearing and the Ear Hearing and the Ear
- 13. ïź Resonance occurs in the inner ear. Resonance occurs in the inner ear. ïź A wave of a particular frequency causes a specific part A wave of a particular frequency causes a specific part of the basilar membrane to vibrate. of the basilar membrane to vibrate. ïź Hair cells near the part of the membrane that vibrates Hair cells near the part of the membrane that vibrates then stimulate nerve fibers that send an impulse to the then stimulate nerve fibers that send an impulse to the brain. brain. Hearing and the Ear, Hearing and the Ear, continued continued
- 14. The Ear The Ear
- 15. Musical Instruments Musical Instruments ăHow do musical instruments make How do musical instruments make sound? sound? ăMost instruments produce sound Most instruments produce sound through the vibration of strings, air through the vibration of strings, air columns, or membranes. columns, or membranes.
- 16. Musical Instruments Musical Instruments ïź Musical instruments rely on standing waves. Musical instruments rely on standing waves. ïź Standing waves can exist only at certain Standing waves can exist only at certain wavelengths on a string. wavelengths on a string. ïź The primary standing wave on a vibrating The primary standing wave on a vibrating string has a wavelength that is twice the length string has a wavelength that is twice the length of the string. of the string. ïź The frequency of this wave is called the The frequency of this wave is called the fundamental frequency. fundamental frequency.
- 18. Musical Instruments, Musical Instruments, continued continued ïź Instruments use resonance to amplify sound. Instruments use resonance to amplify sound. ïź Resonance: Resonance: a phenomenon that occurs when a phenomenon that occurs when two objects naturally vibrate at the same two objects naturally vibrate at the same frequency frequency ïź natural frequencies: natural frequencies: the specific frequencies at the specific frequencies at which an object is most likely to vibrate which an object is most likely to vibrate ïź The natural frequency of an object depends on The natural frequency of an object depends on the objectâs shape, size, mass, and the material the objectâs shape, size, mass, and the material from which the object is made. from which the object is made.
- 20. ă How are the reflections of sound waves used? How are the reflections of sound waves used? ă Reflected sound waves are used to determine Reflected sound waves are used to determine distances and to create images. distances and to create images. ïź Some ultrasound waves are reflected at boundaries. Some ultrasound waves are reflected at boundaries. Ultrasound and Sonar Ultrasound and Sonar
- 21. ïź Ultrasound imaging is used in medicine. Ultrasound imaging is used in medicine. âą The echoes of very high frequency The echoes of very high frequency ultrasound waves, between 1 million and ultrasound waves, between 1 million and 15 million Hz, are used to produce 15 million Hz, are used to produce computerized images called computerized images called sonograms sonograms. . Ultrasound and Sonar, Ultrasound and Sonar, continued continued
- 22. ïź Some ultrasound waves are reflected at Some ultrasound waves are reflected at boundaries. boundaries. ïź Some sound waves are reflected when they pass Some sound waves are reflected when they pass from one type of material into another. from one type of material into another. ïź How much sound is reflected depends on the How much sound is reflected depends on the density of the materials at each boundary. density of the materials at each boundary. ïź The reflected waves can be made into a The reflected waves can be made into a computer image called a computer image called a sonogram. sonogram.
- 23. ïź Sonar is used to locate objects underwater. Sonar is used to locate objects underwater. ïź Sonar: Sonar: s sound ound n navigation avigation a and nd r ranging, a system anging, a system that uses acoustic signals and echo returns to that uses acoustic signals and echo returns to determine the location of objects or to determine the location of objects or to communicate communicate ïź A sonar system determines distance by A sonar system determines distance by measuring the time it takes for sound waves measuring the time it takes for sound waves to be reflected back from a surface. to be reflected back from a surface. d d = = vt vt Ultrasound and Sonar, Ultrasound and Sonar, continued continued
- 24. Sonar Sonar