Sound Waves Speed Intensity Loudness Frequency Pitch Resonance 13.2 Sound Waves
Sound Waves Sound waves are longitudinal waves. Behaviors of sound can be explained with a few properties: Speed Intensity Loudness Frequency Pitch
Sound Waves In dry air at 20ºC, the speed of sound is 340 m/s. (660 mph) Sounds waves travel: faster in solids slower in liquids slowest in gases This is due to the particles in a solid are close together and the speed of sound depends directly on the density of the medium.
Sound Waves
Intensity and Loudness How does intensity, loudness, frequency and pitch affect sound waves? Intensity The amount of energy an sound wave carries per second through a unit area. Sound intensity depends of the waves amplitude and distance from the sound source. Example: When someone whispers in your ear, the sound intensity may be greater than when someone shouts at you from the other end of a field.
Intensity and Loudness Loudness The sound level describing what you actually hear. A sound wave of greater intensity sounds louder As intensity increases, loudness increases Varies per person s health of ears and how your brain interprets information.
Intensity and Loudness A sound wave with a higher amplitude and energy is perceived as a louder sound. A sound wave with a lower amplitude and energy is perceived as a softer sound.
Measuring Sound Intesity Sound Intensity is measured in decibel (db) Normal room conversation is: 40-50 db Damage to your ears: above 85 db Pain will occur at: 120 db
Measuring Sound Intesity
Measuring Sound Intesity
Frequency and Pitch Frequency The number of vibrations that occur per second in a sound wave. Measured in Hertz. A frequency of 50 Hz means 50 vibrations per second. Pitch Description of how high or low the sound seems to a person Pitch depends on the frequency of a sound wave o High frequency means high pitch o Low frequency means low pitch
Frequency and Pitch (Music) Musical instruments are examples of objects producing different frequencies The trumpet can produce higher frequency by changing the length of the tubing which air moves The longer the tube, the longer the wavelength, the lower the frequency of the note produced
Frequency and Pitch (Music)
Frequency and Pitch (Music) Which tube has the highest pitch sound? The shortest tube Which tube has the lowest pitch sound? The longest tube
Sound Levels Most people can hear between 20 hertz and 20,000 hertz Infrasound (0-20 Hz) is sound at frequencies lower than most people can hear Ultrasound (20,000 Hz and above) is sound at frequencies higher than most people can hear
Resonance Certain devices create strong sound waves at specific natural frequencies. If another object has the same natural frequency is impacted by these sound waves, it may begin to vibrate at this frequency as well. One object emitting a sound wave with a specific frequency causing another object to vibrate with same frequency is know as resonance.
Resonance The Opera Singer Breaking a glass by singing a high-pitched note Singer creates a sound wave that matches the natural frequency of the glass Glass resonates (vibrates) at same frequency so energetically that it shatters. https://www.youtube.com/watch?v=rrzt7xo5kn4
Resonance Example #1 A dampened fingertip rubbed around the rim of a crystal glass causes the glass to vibrate and produce a musical note. This effect is due to: a. Resonance b. Refraction c. Reflection d. Rarefaction
Resonance Example #2 Resonance occurs when one vibrating object transfers energy to a second object causing it to vibrate. The energy transfer is most efficient when, compared to the first object; the second object has the same natural: a. Loudness b. Amplitude c. Frequency d. Speed
Resonance Example #3 A car traveling at 70 km/hr accelerates to pass another car. When the car reaches a speed of 90 km/hr, the driver hears the glove compartment door start to vibrate. By the time the speed of the car is 100 km/hr, the glove compartment door has stopped vibrating. This vibrating phenomenon is an example of: a. Destructive interference b. Diffraction c. Resonance d. Rarefaction
Resonance Example #4 What is the wavelength of a 256-hertz sound wave moving in air? a. 1.17 10 6 m b. 1.33 m c. 0.753 m d. 87,040 m
Resonance Example #5 Frequency lower than the human ears can hear a. Loudness b. Intensity c. Ultrasound d. Pitch e. Infrasound
Resonance Example #6 This property depends on factors such as your age and the health of your ears a. Loudness b. Intensity c. Ultrasound d. Pitch e. Infrasound
Resonance Example #7 This property is measured in units called decibels a. Loudness b. Intensity c. Ultrasound d. Pitch e. Infrasound
Resonance Example #8 What do musical instruments vary to produce different sounds? a. Loudness b. Intensity c. Ultrasound d. Pitch e. Infrasound
Resonance Example #9 Frequency higher than the human ear can hear a. Loudness b. Intensity c. Ultrasound d. Pitch e. Infrasound