The Science of Sound

The Science of Sound


Sounds of Laughter, Shades of Life The birds do it. The bees do it too and so do you. An amazing range of animals generate sound: pressure waves caused by displacing the medium in which they travel.


Tiny Noisemaker You may think that’s the screaming baby across the airplane aisle, but human speech is at a comfortable 60 dB. The decibel, named after Alexander Graham Bell, is logarithmic in scale: an increase of 10 dB is actually ten times as loud. Anything above 85 dB is dangerously painful and the loudest sound tolerated by the human ear is 120 dB.  The loudest animal is the sperm whale at an ear-splitting 236 dB! But the prize for the biggest bang for buck goes to the lesser water boatman: perhaps in protest of its diminutive size and name, it is the loudest animal for its body size (see graph; listen here: Fortunately, the surrounding water dissipates 99% of its mating call or it would sound like a freight train hurtling by.  Shakespeare may dismiss life as a tale told by an idiot, full of sound and fury, signifying nothing , but to a female water boatman, the call of her mate is irresistible. Especially since he generates the sound by rubbing his…ahem.. sexual appendage against his abdomen. The lesser water boatman’s call is an example of runaway evolution since there is apparently no penalty paid for the price of loudness in his case.


Cheers to your Ears Astonishingly, the actual displacement of molecules in the air is tiny- about  11μm or 1/7th the thickness of a piece of paper at 120 dB! Did you know that the faintest sound the human ear can detect corresponds to a displacement of air molecules by ~1.1 x 10-11 m, or 11 picometers– about 1/10 the radius of a mid-sized atom? Not only can the human ear detect vibrations with a sensitivity that spans six orders of magnitude, it can also detect sounds across nearly a 10 octave range of frequencies.


Movie Soundtrack : Across The Universe + Helter Skelter (Across The Universe)

Sounds of laughter, shades of life

Are ringing through my opened ears

Inciting and inviting me.

Limitless undying love, which

Shines around me like a million suns,

It calls me on and on across the universe


• Whacky video on how we hear: Fun Science: Sound

• Cool Info on Sound:


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101 Responses to The Science of Sound

  1. Some sound thinking, Rajini Rao …

  2. Rajini Rao says:

    Just making some tiny waves, William McGarvey …

  3. So in reality, it is more than just a bunch of noise! 😉 very interesting Rajini Rao thanks!

  4. Matt McIrvin says:

    Anything that can beat a cicada in a noise competition has my respect.

  5. My thoughts exactly Matt McIrvin

  6. Rajini Rao says:

    Fortunately, this lesser water boatman lives on the river bottom although we can still hear it chirp when walking along the river bank. The chorus of cicadas on a summer night is quite deafening, isn’t it!

  7. Not only is this boatman loud, it makes the sound with its PENIS! Now THAT is a true showing of virility!

  8. Rajini Rao says:

    Haha, Robert Ferentz , I was trying to be discreet 🙂

    Technically, it is described as a sexual appendage to grasp the female. Perhaps an insect expert can help us out .. Chris Mallory?  According to the paper, “The sound is produced by rubbing a pars stridens on the right paramere (genitalia appendage) against a ridge on the left lobe of the eighth abdominal segment”. But yes, penis might work too 🙂

  9. The wiki page explicitly said a ridge on its penis, so I went explicit too 🙂

  10. E.E. Giorgi says:

    cool! I would’ve thought we’d be the loudest… has anybody ever been to Valencia, Spain? (er… no offense to the Valencians of course…)

  11. Rajini Rao says:

    LOL, E.E. Giorgi ! Tagging Víktor Bautista i Roca for his Catalan perspective 😉

    I’ve been to Valencia, lost in the old part of town after midnight with not much knowledge of Spanish, yikes!

  12. Chad Haney says:

    Rajini Rao the last paragraph is exactly why the dB scale is logarithmic. Did you hear the crazy birds in my video?

    Talking Heads

  13. Rajini Rao says:

    Thanks for the link..I need to catch up on all your posts, Chad Haney ! I love that bird call..wonder what they are?

  14. Rajini Rao says:

    I couldn’t read the writing on the can, Norman Robinson 🙂

  15. Gaurav Gupta says:

    Nice so beautiful Rajini

  16. Hi …Rajini..

    Gud nite ….Sweet dreams. .

  17. Gaurav Gupta says:

    Hiii Rajini How r u..


    Happy Teddy Day Friend

  18. Wesley Yeoh says:

    thank goodness for scale!

  19. Carlos Jaen says:

    I dont see my last ex on that graph.

  20. Rajini Rao says:

    LOL, Carlos Jaen . Perhaps she had a problem with his her, er…appendage (noise making one, of course!) 😀

    Edit: oops, got the gender of your ex wrong, sorry!

  21. Carlos Jaen says:

    No no, Raj, her record breaking sounds had more to do with remote control possession, and frequency of operation.

  22. Rajini Rao says:

    Haha, I trust you have regained control of the remote now? 😀

  23. Kawthar A says:

    Hey Rajini Rao 😉

    Interesting post, and I always thought the mosquito is the worst 🙂

  24. Rajini Rao says:

    I remember the mosquito in your room, Kawthar AL ABDALLA 😉

  25. Carlos Jaen says:

    Yes, pyrrhic victory, i have the remote, but lost possession of kitchen, house finances, and orderly life !

  26. Kawthar A says:

    “I will find you, and I will KILL you” 😀

  27. Clever little fellow, that Lesser Water Boatman! Especially given the method of sound generation – as an experiment, I tried this, but it didn’t make much sound at all. ;-)

  28. Rajini Rao says:

    ROFL, David Archer . I hope you were home. If not, call for bail money.

  29. “For Science!” is all the legal protection I need, Rajini Rao. 


  30. Chad Haney says:

    You are doing it wrong David Archer 

  31. I bet I’d have better volume using someone else’s abdomen! (This must stop soon!)

  32. Chad Haney says:

    Except for David Archer, the sword isn’t as loud. 

  33. I can’t help but wonder if the size of the appendage affects its performance.  And how sad that this poor insect must endure being called “lesser”. 

  34. Rajini Rao says:

    Shannan Muskopf  The whole area that generates this loud sound is only 50 μm in area, which makes it all the more extraordinary. A “regular” water boatman is around 20 mm in length, so this one is a tenth in size 🙂

  35. Not to nit pic, but increasing the SPL by 10db doesn’t make it 10 times as loud, it is perceived by the brain as being twice as loud.

  36. E.E. Giorgi says:

    Rajini Rao : have you been to Valencia in March, for Fallas? I think they break the bearable sound threshold…

  37. Rajini Rao says:

    E.E. Giorgi , it wasn’t during the festival but I can imagine..having been through the din of Indian festivals. Apparently, the idea is to chase away the demons during the most auspicious moments of Hindu ceremonies (including weddings)..never mind if a few human ear drums are lost along the way 😛

  38. E.E. Giorgi says:

    funny, I guess you don’t hear demons or anything else after that… 🙂

  39. Rajini Rao says:

    You know, that’s one way to make a marriage last 😉

    The marriage ceremony goes on for three days (did I mention the holy fire that makes one cry?). That’s an ordeal that no one wants to repeat! 

  40. E.E. Giorgi Rajini Rao Never been in València during falles, but two of my grandparents were Valencian, so I’m quite used to gunpowder explosions. And in Catalonia we have also quite noisy traditions, as Saint John’s night.

    Also, in many villages, during the saint patron’s festival, is quite usual to be awaken by the “trabucaires”. A trabucaire is the one who shots a “trabuc”, an ancient gun. There’s on Catalan village that, on 30 December, can have something beteween 100 and 200 trabucaires together, on the “pine festival”, a really surrealist tradition. 

    In this video you can see (well, in the middle of the smoke) the tree and hear the trabucaires shoting. If you wait till the end, you’ll see how they make a “wave”. LA FESTA DEL PI DE CENTELLES

    When I’ve said the festival is surrealist is mostly because of the ending. The top of a pine is lifted, hanging upside down inside a church, over the altar, with nets of apples and cookies in the shape of stars and full moons hanging from it while the whole village shouts (more than sings) the saint patroness (santa Coloma) hymn.

    Here you can have a feel of most of the festival: Festa del pi de Centelles

  41. Here you have a “traca” (enchained fireworks?) in a Valencian town, Aldaia (first minute of the video) TRACA CORREGUDA TRAMS DE TRONS ALDAIA 2007 You have a smaller one (but longer and “interactive) at 3:30.

    And here you have some images from a “correfoc” (fire-run?), derived from ancient “balls de diables” (devils’ balls, dances). Correfoc Festes de la Mercè 2012 (HD)

    As you can see, we Catalan speaking people love fire, gunpowder and loud noise.

  42. Awesome Rajini Rao Thanks

  43. Ow, and another ancient tradition, cultural heritage by the Unesco, with fire and some noise, the Patum of Berga. In the video you can not apreciate it, but the people with the fired are covered from head to toes with branches and leaves. Els Plens de la Patum de Berga

  44. Rajini Rao says:

    Víktor Bautista i Roca , thanks for the fantastic video links and information. I just finished watching the pine tree being felled and pulled by oxen..the noise and smoke, and the colorful red caps. Checking out your other links..

  45. Rajini Rao says:

    John Christopher , thanks for lending me your ear 🙂

  46. …”Falles”???  I thought it was spelled “P-h-a-l-l-us”… did I miss something in my …speed reading?

  47. Rajini Rao says:

    LOL, where is this John Christopher ? In one of the comments or in a link?

  48. Actually I saw it spelled two different ways in the comments above, about Valencia… Rajini Rao 

  49. John Christopher In singular is “falla”. If you make the plural the English way it would be fallas, but in Catalan it’s “falles”.

  50. Bill Collins says:

    So humans can hear atoms move? Is that the gist of that statement about six orders of magnitude? Whoa.

  51. Rajini Rao says:

    Bill Collins , as long as the air displaced by the moving atom or whatever can impact the eardrum: “The ear drum only has to move less than the diameter of a hydrogen atom for us to perceive sound.” I had not realized that human hearing was quite that good! I just learned that we can hear even better under water when we perceive vibrations with the mastoid bone (behind our ear)! See:

  52. Bill Collins says:

    I will read it. Thanks!

  53. Rajini Rao What do you think about our noisy traditions? I guess from your eyes they are quite exotic 🙂

  54. Rajini Rao says:

    Víktor Bautista i Roca , I love these cultural eccentricities of each is what makes us uniquely human 🙂

  55. E.E. Giorgi says:

    wow, Víktor Bautista i Roca thanks for all the background, it’s fascinating! yeah, I hated tracas with a passion when I was there… 🙂 

  56. Kindly send articles theoretical and empirical conclusions madam. A provision for saving on the wall of the post is gratefully acknowledged.

  57. hello dear  rajini rao

  58. can i wan to tallk about a matter?

  59. Rajini Rao Hey, we are not eccentric, it’s the rest of the wold, who is weird! 😉

  60. impresionante, la relación de proporción inversa del sonido respecto al tamaño, asi que, el tamaño si importa. gracias por la información Rajini

    impressive, the relationship of inverse proportion to the size of the sound, so, size does matter. thanks for the info Rajini

  61. Write/send more such information which could be used academical y but lazy people like me find it lugubrious to search

  62. This really reminds me, gravity dominates, cos, in the nature, the smaller the weight, the faster it moves.

  63. Mary T says:

    Great post Rajini Rao ~ Somehow, my mind keeps returning to one thing…..Benedict Cumberbatch ;D.

  64. Rajini Rao says:

    Mara Rose , Mr. Cumberbatch would win the prize for the most delicious sound 🙂

    For any on this thread who doubt: John Keats- Ode to a Nightingale

  65. Chad Haney says:

    I assume you are limiting the prize competition to actors because I recall a certain someone who enjoys Mr. Frampton and Mr. Morrison.

  66. Rajini Rao says:

    Le sigh. Now everyone knows of my acoustical promiscuity 🙂

  67. Chad Haney says:

    Well we didn’t say anything about their appendages.

  68. Rajini Rao says:

    LOLOL! I’m accusing Mr. Nudibranch of holding back. “When it mates, it extrudes around a centimetre of penis, but the full organ is three centimetres long.” He ought to let it all go, never mind the consequence.

  69. Rajini Rao says:

    As Gnotic Pasta knows quite well 🙂

  70. Rajini Rao says:

    We are all ears, Gnotic Pasta 🙂 Glad you made it home safe!

  71. Rajini Rao says:

    Excellent share, thank you Josyula Krishna !

  72. Thomas Kang says:

    I don’t mean to feign innocence here, but when I saw the words “water boatman” the first thought that came to mind was the ferryman in Siddhartha and the sound om, not some funky insect making noises with his penis.

    Having said that, I never knew what a water boatman was, but what an interesting insect! I just learned about it from this post and here (, which offers up a list of top 10 noisiest critters.

    Is a water boatman related to aphids? Also, what are those little insects called that sort of walk on water. That’s what I was expecting to see.

  73. Rajini Rao says:

    Hi Thomas Kang , you are probably thinking of the water strider as the little insect that walks on water. It’s just surface tension in play. Science Friday did a great video on it, if you can do a search. I believe I posted it a long time back, maybe. 

  74. Thomas Kang says:

    Thanks, Rajini! I can count on you to have already done a post on nearly half of all the things in the natural world I suddenly become curious about. I wish I knew the names of more plants and animals. 

  75. Thomas Kang says:

    Sure, my kids, Peter, but me too; I’m the perfect age! All I need are 36-hour days.

  76. Rajini Rao i came to find you to see if you were posting on the mela & i see that you have been away since Feb 10.  Are you in India?  I posted something instead using a photo from last time.  No one here knows anything about the mela.  It is funny, they know the haj but not the mela…

  77. Rajini Rao says:

    Hi nomad dimitri , I’m here but lurking ..been busy with work. Checking out your Kumbh Mela post…

  78. Rajini Rao i can only imagine how busy you are.  feel free to correct what i have: it is very simplified but i had to keep it simple if anyone was going to understand anything…


  79. And – yet another great name for a band: “The Pistol Shrimps”!

  80. Rajini Rao says:

    Johnny Crawfish and The Sex Pistol Shrimps?

    That was quite an extraordinary video clip, thanks Feisal Kamil .

  81. Rajini Rao says:

    Haha, excellent point Peter Lindelauf . Eventually the topic does meander back.

  82. Feisal Kamil And strangely topical in more than one way. 

  83. EmPe Ah says:

    Please insert my upstairs neighbor into this chart. I haven’t done scientifically accurate measuring yet but am sure he should be placed somewhere between “Lesser Water Boatman” and “Snapping Shrimp”. In fact coming to think of it, he looks a bit like a “Lesser Shrimp”…..

  84. Really fun post- Love that sound bite of the Lesser water boatman.

  85. what are the units of DB/body-size (volume or mass?)…. very curious about the dimensions….

  86. they haven’t heard the decibel of the girls above me apparently.

  87. did you know what time of year they hatch Rajini and their native habitat?

  88. Rajini Rao says:

    The males (!) who generate this cacophony are way under water, in river beds, but can be heard by a person walking along the bank. They use this as a mating call..not sure of the season (summer, would be a good guess).

  89. aquatic macro eh, some fascinating stuff Ranjini. My brother just did a study of macro invert. on McMichael’s Creek in the Poconos (canopy vs. open area). Seen hatches before? Whole other universe in an aquatic environment.

  90. Sorry, for some reason I want to write Ranjini, force of habit I guess. This is the kind of hatch I want my brother to film – ‘s why I got him a small handheld video camera for Christmas.   

  91. Rajini Rao says:

    I hope he shares some of his videos here, Bradley Hartzler . Ranjini is a bona fide name, close enough..sometimes I get called Regina 🙂

  92. We’ll see, Springtime. He’s quite a good photographer, this is the logical next step for him. You’ll be the first I send them to to promote. Blessings, Bradley John Hartzler

  93. Rajini Rao says:

    I’ll be glad to share them here, and via some Science Pages on G+. Cheers!

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