1 - sound in the brain Flashcards
What is a sound wave?
Movements or vibrations of an object cause pressure changes in air, water or any elastic medium that can transmit virbrations.
What are pure tones?
Pure tones are made out of air pressure changes that occur in a sine wave pattern.
What is frequency?
Frequency is the number of cycles per second that the pressure changes repeat. It is described in Hz where 1Hz is one cycle per second. Higher frequency = higher pitch
What is amplitude?
Amplitude is the size of the pressure change. It is described in dB and a higher amplitude = higher volume.
What are complex tones?
Complex tones are a bunch of pure tones (harmonics) added together. The first harmonic is the fundamental frequency of the tone aka the repetition rate of a complex tone. The higher harmonics are the fundamental frequency of a tone times a whole number
Why did an audibility curve have to be created?
Because loudness not only depends on the decibels (amplitude) but also on the frequency. Some frequencies have low thresholds, while others have high thresholds.
Where lie the tones we can hear?
These lie in the auditory response area which lies between the audibility curve and the threshold of feeling.
What is the effect of the missing fundamental?
If one fundamental or other harmonics are missing - the pitch remains the same
What is resonance in the auditory canal?
Resonance occurs in the auditory canal when sound waves are reflected back from the closed end of the auditory canal. These interact with sound waves that are entering the canal and reinforce some of the sound’s frequencies.
Why are ossicles needed?
The inner ear is filled with a liquid that is denser than air. Pressure changes in the air are poorly transmitted to the much denser liquid. Therefore the ossicles help the problem by concentrating the vibration of the large tympanic membrane onto the much smaller stapes increasing the pressure by a factor of 20.
How does vibration bend the stereocilia?
The up-and-down movement of the basilar membrane causes the organ of Corti to move up and down and the tectorial membrane to move back and forth. this causes the stereocilia of outer hair cells that are embedded in the membrane to bend. The others bend in response to pressure waves in the liquid.
How does the bending of stereocilia cause electrical signals?
When they bend in one direction, the tip links stretch and tiny ion channels open which allow positively charged potassium to enter which eventually causes an electrical signal. If they bend in another direction the tip links slacken, the ion channels close and the ion flow stops. the back and forth bending cause alternating bursts of electrical signals and no signals.
What is phase locking?
Firing at the same place in the sound stimulus
Where does the fourier analysis happen in the auditory pathway?
In the basilar membrane. It vibrates like a wave and it vibrates at different places at the frequency of a harmonic. One spot that vibrates the most is the fundamental frequency.
Cochlea and frequency
Frequency increases from the apex to the base of the cochlea. The apex is the lowest frequency and the base is the highest frequency.
