Sensation and Perception – Part II: Hearing

Amplitude Frequency

Dude, you’re so sensitive… Amplitude: “loudness” - determined by the amplitude of sound waves (how tall the waves are) High amplitude, loud sounds. “Loudness” is subjective based on how sensitive your ears are to the amplitude of sound.

Like nails on a chalkboard… Frequency: Refers to how many sound waves occur within one second. High frequency, high pitch (sound waves close together) Low frequency, low pitch (sound waves far apart)

True or False? If you want to instantly improve your hearing, do what your mother tells you and clean out your ears of ear wax!

False! The wax does not affect your hearing at all! Your ear is literally a hole in your head, and just like boogies in your nose, you need wax to keep it protected from the outside world. Btw, you don’t ever need to clean out your ears, but sometimes it is necessary, like before a hot date!

True or False? Headphones are only dangerous to your ear health if the volume is too loud.

False! Yes, loud music causes permanent damage to hearing. But not only that, using ear buds or noise-cancelling headphones increases the bacteria in your ear by 700x in just one hour! Yay ear infections!

Measuring Sound Amplitude is measured in decibels (dB). Decibels: scientific units that measure “loudness” Humans carry a threshold of 0 dB (absolutely no sound) to 140 dB (pain and permanent hearing loss)

Decibel Level of Some Common Sounds Decibels Source Exposure Danger 180 Space shuttle launch Hearing loss certain within 150 feet of launch pad 140 Jet aircraft motor Any exposure dangerous 120 Sandblaster, thunderclap, average Freshmen class in a hallway. Immediate danger 100 Heavy auto traffic, lawn mower 2 hours 80 Alarm clock, average mp3 player volume 1 hour 60 Normal conversation No danger 30 Quiet library 20 Soft whisper Minimal detectable sound

True or False? Babies cry so loud because their hearing is terrible when they are born.

False! Babies cry for numerous reasons, but definitely not to hear themselves better. Their hearing is actually much, much better than adolescents or even toddlers. Their hearing ability decreases over time as other senses improve with normal child development.

The Ear Preview Question 9: How does the ear transform sound energy into neural messages?

The Ear Outer Ear: Collects and sends sounds to the eardrum.

The Ear Middle Ear: Chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window.

The Ear Inner Ear: Innermost part of the ear, containing the cochlea and semicircular canals.

Inner Ear Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals. Semicircular canals: look like little loops; contain fluid that tell your parietal lobe where your head is in relation to gravity. This controls your balance and keeping your head upright. So what’s up with motion sickness and dizziness?

Localization of Sounds Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. Preview Question 11: How do we locate sounds?

1. Intensity differences Localization of Sound 1. Intensity differences 2. Time differences Time differences as small as 1/100,000 of a second can cause us to localize sound. The head acts as a “shadow” or partial sound barrier. Preview Question 12: What are the common causes of hearing loss, and why does controversy surround cochlear implants?

True or False? Elephants can “predict” an earthquake because they can hear with their feet.

True!... …kind of. Elephants can feel seismic vibrations in their feet over very long distances, which is why they “trumpet blast” so close to the ground. They can feel an earthquake way below ground before we humans can!

You never stop hearing, not even in your sleep. True or False? You never stop hearing, not even in your sleep.

True! So there’s no reason to miss your wake up alarm! Your ears are constantly picking up sound, except during sleep your temporal lobe is not actively analyzing the sound. (“What was that?!”)

Hearing Loss There are two types of hearing loss: Conduction hearing loss Sensorineural hearing loss

Conduction Hearing Loss Occurs when there are physical problems sending sound waves through the outer or middle ear Often involves a punctured eardrum or damage to any of the bones in the middle ear Hearing aids Common treatment for conduction hearing Tiny instruments worn just inside the outer ear Change sound waves into amplified vibrations and send them to the inner ear

Sensorineural Hearing Loss More common than conductive hearing loss Involves nerve problems in the inner ear Often occurs because hair cells in the cochlea are damaged either by disease, injury, or aging Cochlear implant Only means of restoring hearing Miniature electronic device surgically placed into cochlea Changes sound waves into electrical signals Best candidates—young children born with hearing loss