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Hearing Sound Have you ever felt sound? Have you ever felt sound? Car with really loud music playing (especially with heavy base). Did you know? Thunder and lightening are essentially the same event? Did you know? Thunder and lightening are essentially the same event? How can this be????? Did you know? Thunder and lightening are essentially the same event? How can this be????? Light travels at 299,792 m/sec. Sound travels at 335 m/sec. Can humans or animals hear better? Can humans or animals hear better? Remember that sound is a vibration. Can humans or animals hear better? Remember that sound is a vibration. Well….the frequency of a sound wave is the number of vibrations (waves) per second. Can humans or animals hear better? Remember that sound is a vibration. Well….the frequency of a sound wave is the number of vibrations (waves) per second. We measure this in something called a Hertz (Hz). Can humans or animals hear better? Remember that sound is a vibration. Well….the frequency of a sound wave is the number of vibrations (waves) per second. We measure this in something called a Hertz (Hz). 1Hz = 1 wave per second Can humans or animals hear better? Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Dogs can hear up to about 25,000 Hz. Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Dogs can hear up to about 25,000 Hz. Cats can hear up to about 65,000 Hz. Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Dogs can hear up to about 25,000 Hz. Cats can hear up to about 65,000 Hz. >20,000 Hz = ultrasonic. Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Dogs can hear up to about 25,000 Hz. Cats can hear up to about 65,000 Hz. >20,000 Hz = ultrasonic. <20 Hz = infrasonic. Can humans or animals hear better? Humans hear from about 20 to 20,000 Hz. Dogs can hear up to about 25,000 Hz. Cats can hear up to about 65,000 Hz. >20,000 Hz = ultrasonic. <20 Hz = infrasonic. Elephants communicate at this level. Some common noises: Some common noises: 20 (dB) = whispers Some common noises: 20 (dB) = whispers 40-50 (dB) = Average home Some common noises: 20 (dB) = whispers 40-50 (dB) = Average home 70 (dB) = City street Some common noises: 20 (dB) = whispers 40-50 (dB) = Average home 70 (dB) = City street 115 (dB) = rock concert Some common noises: 20 (dB) = whispers 40-50 (dB) = Average home 70 (dB) = City street 115 (dB) = rock concert 140-170 (dB) = jet engine Some common noises: 20 (dB) = whispers 40-50 (dB) = Average home 70 (dB) = City street 115 (dB) = rock concert 140-170 (dB) = jet engine 85 (dB) or higher for extended periods of time can cause permanent hearing loss Ear Canal The human ear: Parts of the ear The human ear: Parts of the ear Outer ear: funnels sound waves. The human ear: Parts of the ear Outer ear: funnels sound waves. Ear canal: a few cm long and ends at the eardrum. The human ear: Parts of the ear Outer ear: funnels sound waves. Ear canal: a few cm long and ends at the eardrum. Eardrum: A small, tightly stretched, drum-like membrane that vibrates when hit by sound waves. The human ear: Parts of the ear Middle ear: Contains the three smallest bones in the human body. The human ear: Parts of the ear Middle ear: Contains the three smallest bones in the human body. Hammer: Attached to the eardrum and vibrates and hits the anvil. The human ear: Parts of the ear Middle ear: Contains the three smallest bones in the human body. Hammer: Attached to the eardrum and vibrates and hits the anvil. Anvil: shakes the stirrup. The human ear: Parts of the ear Middle ear: Contains the three smallest bones in the human body. Hammer: Attached to the eardrum and vibrates and hits the anvil. Anvil: shakes the stirrup. Stirrup: vibrates against the membrane separating the middle and inner ear. The human ear: Parts of the ear Inner ear: Separated from middle ear by a membrane. The human ear: Parts of the ear Inner ear: Separated from middle ear by a membrane. Cochlea: cavity of the inner ear filled with liquid and Lined with thousands of tiny hairs. The human ear: Parts of the ear Inner ear: Separated from middle ear by a membrane. Cochlea: cavity of the inner ear filled with liquid and Lined with thousands of tiny hairs. The vibrations are passed from stirrup to membrane to liquid to hairs (which sway back and forth). The human ear: Parts of the ear Inner ear: Separated from middle ear by a membrane. Cochlea: cavity of the inner ear filled with liquid and Lined with thousands of tiny hairs. The vibrations are passed from stirrup to membrane to liquid to hairs (which sway back and forth). The hairs are attached to nerve cells that detect movement and send messages to the brain. Applications of Sound: Sonar: (Sound navigation and ranging). Measuring the time it takes to detect a reflected sound wave. Applications of Sound: Ultrasound and infrasound: Dog whistles (ultrasonic) Elephants stomping on the ground (produce sound waves too low for humans to hear). (infrasonic) Applications of Sound: Ultrasound (Echolocation): Using sound waves to determine distances or locate objects. Dolphins Bats Applications of Sound: Ultrasound (other uses): Medicine Brushing your teeth Jewelry cleaners Some cameras (automatic focus)
