episode38

038 How We Hear Different Pitches

Leslie Samuel IBTV, Physiology, Sense Organs 105 Comments

Some people sing high, others sing low. There are so many pitches, which are the result of different sound wave frequencies.

How does the ear allow you to distinguish between these various pitches? Watch this video and listen as Leslie details the processes in the inner ear that result in us being able to tell the difference.

Enjoy!

Transcript of this Episode

“Aaa! Aaa!  Aaa! Aaa!” (high tone to a deep tone) Hello! Welcome to another episode of Interactive Biology TV where we’re making Biology fun. My name is Leslie Samuels and I apologize for what you had to listen to at the beginning of this episode. In this episode, episode 38, I’m going to talk about how we hear different pitches. And what do mean by different pitches? I’m glad you asked. I mean, “Aaa! Aaa! Aaa!” (high to low pitch).

I’m sorry, I apologize. I shouldn’t be putting you through that. But, that is exactly what we’re going to be talking about today. I just made a few different sounds and they were different pitches. We want to look at how your brain is able to distinguish the different pitches based on what is happening inside the ear. So, “Let’s continue,” (high pitch). “Let‘s continue.” (Low pitch).

Here we’re looking at the ear. We’ve looked at this figure in the last episode and we looked at one that was similar to it in the episode before that. Where we ended off last time, we had a signal coming in, and we spoke about how the malleus, incus, and stapes are involved in transferring that signal to the cochlea. What I’m going to do now is, I’m going to take this cochlea and I’m gong to roll it out and just kind of extend it.

So, we’re not going to look at it like how it looks here, kind of like a snail. We’re going to look at it as if was just rolled out. So, let’s go to the next picture.

Here we have it. We have the cochlea that we unrolled and now it extends right here. What you’ll see is, here we have a membrane that we call the basilar membrane, and here’s the writing for that right here. This is the basilar membrane. What you’re going to notice about the basilar membrane is it’s thinner over here than it is over here.

So, at this end, it’s significantly thinner and as it goes away from the oval window where the malleus, incus, and stapes connect, as it goes away from that section, it gets thicker and thicker and thicker until it’s thickest right here at this end.

What you’re going to see here is, we have a number of frequencies that are associated with these different sections. Here we have at 25 Hz which is a low frequency, and as we come over to the thinner section, we have higher frequencies up here to 1600 Hz. And, it goes all the way up here to about 20 kHz. So, we go as low as 25Hz and as high as 20kHz.

If you’ve taken a Physics class, you know that higher pitches are the result of higher frequencies. Forgive my writing there again. So, higher pitches are the result of higher frequencies and lower pitches are a result of lower frequencies. And, we’re talking about the sound waves, the frequency of the sound wave.

If a certain sound comes into the ear, causes the tympanic membrane to vibrate, the malleus, incus, and stapes vibrate, and that causes the oval window to vibrate, that’s going to cause fluid inside the cochlea to vibrate. Now, depending on the frequency, it’s going to cause a different section of the basilar membrane to vibrate.

Is it easier to move a thinner piece of membrane or a thicker piece of membrane? The answer to that question should be quite obvious. It’s much easier to move a thinner piece of membrane than it is to move a thicker piece of membrane. So, in order for it to vibrate down here, we need more force. You’re going to get a greater force from lower frequencies. Just think about it, if you’re in front of a huge speaker, I mean, massive speaker, and there is sound coming out of that speaker, you’re playing some music, and you’re playing music that has a lot of frequencies. For example, something like this – {nice high frequency music played}.

Now, if you’re standing in front of that huge speaker that’s playing that nice little soft high-frequency music, it’s not going to have a huge effect on you. But, if you start playing something with a lot of bass, something like this – {Music played with lots of bass}.

That’s going to cause you to move. You might even feel the wind of the speaker vibrating and causing the ear to be pushed. You might actually feel that. That’s because when you have lower frequencies, the lower the frequencies, the greater the force that comes along with that frequency.

So, here, in order to cause this to vibrate, we’re going to have a lower frequency sound, which makes sense. That’s why we’re showing 25 Hz here. The closer up we go, where we have the thinner membrane, we can cause that to vibrate with a higher frequency tone. If the frequency is low enough, that might actually cause this entire basilar membrane to vibrate.

The take home message is, depending on the frequency, we’re going to get different regions of the basilar membrane vibrating. This then sends a signal to the brain. Depending on where that signal is coming from, if that signal comes from here and it goes to the brain, that is going to tell the brain that it’s coming from a low frequency and, the brain is going to interpret that as a lower pitch.

If it’s coming from over here, it’s going to the brain, and that’s going to tell the brain that it’s coming from this region which is associated with a higher frequency, and the brain is going to interpret that as a higher pitch.

So, there’s a direct relationship between where it vibrates and where in the brain is being stimulated and depending on where it’s stimulated and where the signal comes from, the brain is going to be able to distinguish between the different pitches. Now, you’re hearing me speak and me speaking right now is a result of a number of different frequencies combining together.

So, there is going to be a complex interaction here, different parts of them is going to be vibrating in different ways, and the brain is going to take all of that and paint the picture of the sound that’s coming from my voice, well, that’s coming from the speakers that you’re listening to this video on and, you can easily distinguish between my, “haa!” (high pitch) and my, “haa!” (low pitch).

I hope that wasn’t too painful and I hope it makes sense. That’s really all for this video. If you have any questions, go ahead and leave them in the comments below. And of course, you can always visit the website at, www.Interactive-Biology.com for more Biology videos and other resources. That’s it for this video and I’ll see you on the next one!

122 comments
Johnf572
Johnf572

This actually answered my drawback, thank you! afkcddacefbf

Justin Malek
Justin Malek

All your videos are very helpful. Even for medical students!

Cila Umat
Cila Umat

Hi, is it possible to make a video on the rate-pitch (phase-locking of the auditory fibres) as well? It will help a lot in the teaching to the students to see the illustration. This video describes the place-pitch very well. TQ.

Melina Harrie
Melina Harrie

I wish you were my audition prof! Wonderfully explained and SO helpful.

Hala El- Khoury
Hala El- Khoury

Your videos are most certainly interactive...not to mention funny! Thanks for putting together educational material in such a great way!

wade mullis
wade mullis

God is amazing for designing something like this.

christine strange
christine strange

I am a professor in Speech-Language Pathology (Communication Sciences and Disorders) and use a few of your videos to supplement the Audiology content in the upper level undergraduate course "Speech and Hearing Science". My Ph.D. is in Voice and Speech Science, and I appreciate the manner in which the content is presented. Very well done, thank you. I believe I may be inspired to create some similar video tutorials in the above mentioned areas. Christine Bergan, Ph.D., CCC-SLP

MrManic MA
MrManic MA

No. You're going to interpret it as a vibration and not as a sound. You're going to feel weird because your ear receives the vibrations, translate it to brain's signals, but your brain can't identify the signals. As a consequence your auditory system is acting like it's going to get information, but nothing happens. For example, when people think that they live in a haunted house, it's because the house is built in an acoustic manner in which the vibrations' frequency are under 20hz.

dbgtvishnu
dbgtvishnu

could you make some anatomy videos for mbbs students on dissection and rememberance notes

dbgtvishnu
dbgtvishnu

your good dude make such more videos its good for students

sara stevens
sara stevens

This is a good question. There is a video by javitsproduction here on youtube entitled "How the ear works", which I believe will solve your question. Skip to 1:51 if you want to get to the part about your question.

sara stevens
sara stevens

This is a good question. I believe this video will help you to understand it better, if you're still interested in it after a month. (skip to 1:51)

sara stevens
sara stevens

This is an awesome video! Why does the cochlea need that liquid, though?

waramasa
waramasa

Thank you, Leslie. I watched 036-038 for the mechanism of hearing, which was really informative.

itsme5900
itsme5900

Frequency and pitch are the same thing, Engineers call it frequency and musicians call it pitch !!

Dylan Bushe
Dylan Bushe

I really enjoy these videos, they help so much hahaa keep it up!

Cristian Cruz
Cristian Cruz

you said that if the frequency is low enough its force can vibrate the whole membrane> so if that happens, does it just sound low or low and high?

mrcrescend066
mrcrescend066

feelin that bass, whats the name of the song?

frimpong alfred brobbey
frimpong alfred brobbey

please I am an audilogy student in ghana and I want the process of hearing to educate my people on how to protect the ear

MrJacobOlson
MrJacobOlson

did anyone notice that the second listening example didn't have any low frequency?

bbbtttify
bbbtttify

please can you make a video about organ of balance ?

Haein Lim
Haein Lim

so... which one of you is right? o_o

Denisey411
Denisey411

omg all your videos are so helpful for my physio class! my teacher sucks ass!! thanks to you I have a shot at passing! thank u!

Mikaxp
Mikaxp

hahahaha great intro.

slab076111
slab076111

This video is great! You should make more on the ear because they are very helpful for students like me who need visual, interactive ways of learning rather then reading a book.

monday2471
monday2471

omg i laughed so hard at 0:37 when he started cracking up

Ighnaz17
Ighnaz17

Nice video and effort, but I have to say that you are wrong with some of the information. As the basilar membrane is getting wider going to the apical end of the cochlea, it is actualy getting less thinner. The explanation about low frequency waves having more energy is also wrong, high frequency waves actually have more energy and that's why they can move the basilar membrane at the basilar end of the basilar membrane.

Andrea
Andrea

just a simple thank you for all these videos.. they are quite helpful :)

ginamolinaa
ginamolinaa

YOU ARE AMAZING!!! thank you soo much for all of these great videos!! :)

Zaimulwaie
Zaimulwaie

I should just skip my physiology lectures and watch your videos instead. it'll save me 52 minutes of my life

Beena
Beena

Hi Leslie, Thank you for these videos-they are brilliant! Beena

Ashley
Ashley

How should this be cited? Contributors, Publisher/Sponsor and the date it was electronically publish? Thank you, it really helped!

Leslie Samuel
Leslie Samuel

Just link to the site and that should be fine :)