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!

Comments 105

  1. InteractiveBiology

    LOL. Glad you enjoyed that rendition in D flat Minor :)

    Yep, Making Biology Fun. It’s the only way to go :D

  2. marazuka

    lolol..loved the beginning..lol.. && the ‘let’s continueee’

    the rest of the vid 2! very helpful..all of them..thnx!

  3. InteractiveBiology

    LOL. I was thinking I should record a CD of me screaming :D

    jk, glad you are finding value in the content. All the best!

  4. katherinependragon

    This is really well done and the diagrams and voice over are so helpful for a student struggling to understand the textbooks! Thanks!!

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  5. gunchibaiyya

    Low frequencies have more energy. Correct.
    Thicker part of the membrane requires more energy to vibrate. Correct.
    That’s why only thicker part of membrane responds to the low frequency. Wrong.

    If the thinner part of the membrane can be moved with little energy, then low frequency sounds should vibrate the thinner part of the membrane as well as the thicker part. Then that means that thinner and thicker both parts respond to low frequency sounds. Wrong.

  6. gunchibaiyya

    Low frequencies have more energy. Correct.
    Thicker part of the membrane requires more energy to vibrate. Correct.
    That’s why only thicker part of membrane responds to the low frequency. Wrong.

    If the thinner part of the membrane can be moved with little energy, then low frequency sounds should vibrate the thinner part of the membrane as well as the thicker part. Then that means that thinner and thicker both parts respond to low frequency sounds. Wrong.

  7. nhyjhane

    i am just curious if what is the name of the fluid in the cochlea and what is the physical stimulus and the receptor of the ear??

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      Lrsamuel

      In the cochlear duct, the fluid is endolymph. In the Scala tympani, it’s perilymph. The stimulus is the vibration of the fluid, which causes the membranes to vibrate and bend the hair cells. You can learn about it in this video.

  8. nhyjhane

    it really helps student like myself!!thanks for your video and knowledge!! i like it very much,, i’m recommending it to my classmates and friends

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      Lrsamuel

      What can happen with age is that your hair cells start getting damaged from being hit over and over with the tectorial membrane. That usually starts in the higher region. When the hair cells stop working in that region, no sound at higher frequencies.

  9. Djalitana

    lets go to the next vid. I hope to hear soon what happens to neurotransmitters and receptors etc. very exiting. thank you so much. is there any reason to have that snail shaped cochlea thing? I mean it could have been done flat or so.

  10. Djalitana

    lets go to the next vid. I hope to hear soon what happens to neurotransmitters and receptors etc. very exiting. thank you so much. is there any reason to have that snail shaped cochlea thing? I mean it could have been done flat or so.

  11. Eric Humphries

    This was a great explanation. Don’t ever stop getting better and better at your communication skills! Thank you for this easy to understand explanation!

  12. InteractiveBiology

    @LittleDanzig You are very much welcome. We appreciate your words of encouragement. Leslie will definitely never stop making more Biology videos to help everyone with their learning. Do keep coming back as we have more videos to be uploaded very soon!

  13. InteractiveBiology

    You are very much welcome. We appreciate your words of encouragement. Leslie will definitely never stop making more Biology videos to help everyone with their learning. Do keep coming back as we have more videos to be uploaded very soon!

  14. InteractiveBiology

    You are very much welcome. We appreciate your words of encouragement. Leslie will definitely never stop making more Biology videos to help everyone with their learning. Do keep coming back as we have more videos to be uploaded very soon!

  15. richyboy230

    You have a lot of detail about the basilar membrane which was massively helpful, and a great easy paced way of explaining things. Thanks for the upload!

  16. InteractiveBiology

    You’re welcome! Glad you understood it well. Please stay tuned. We will have new Biology videos coming very soon!

  17. SpitefulLetters

    hey anyone else finds it slightly funny that when he says pitches it sounds like his insulting you… “this is how you hear different,,,,B***HSSSS!”…Also I’m a medical student , and like these for a quick brush up . cheers

  18. SpitefulLetters

    hey anyone else finds it slightly funny that when he says pitches it sounds like his insulting you… “this is how you hear different,,,,B***HSSSS!”…Also I’m a medical student , and like these for a quick brush up . cheers

  19. strgrl28

    i’m a bit confused according to my text book, the basilar membrane is thickest near the oval window and thinner near the helicotrema. therefore the thickker regions harder to displace explaining why higher frequencies needed to vibrate basilar membrane

  20. strgrl28

    i’m a bit confused according to my text book, the basilar membrane is thickest near the oval window and thinner near the helicotrema. therefore the thickker regions harder to displace explaining why higher frequencies needed to vibrate basilar membrane

  21. strgrl28

    i’m a bit confused according to my text book, the basilar membrane is thickest near the oval window and thinner near the helicotrema. therefore the thickker regions harder to displace explaining why higher frequencies needed to vibrate basilar membrane

  22. Ashley

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

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  23. Zaimulwaie

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

  24. 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.

  25. 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.

  26. 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!

  27. 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

  28. 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?

  29. 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)

  30. 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.

  31. 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.

  32. 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

  33. Hala El- Khoury

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

  34. 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.

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