Part 1

Guitars and Rockets: Surprising Similarity Between

By Tony Phillips Science.NASA.gov posted: 08 November, 2005 7:00 am ET

When the space shuttle lifts off its pad at Kennedy Space Center, the roar is unbelievable. Even miles away onlookers grab their seats and hold on tight. Sound waves penetrate flesh and shake bones.

Recently, country music star Clint Black recorded a public service message for NASA. According to Black, those launches remind him of something: himself.

"Did you know my guitar is like a rocket?" he asks.

Show-business exaggeration? No. It's scientific fact. Black's guitar is like a rocket.

"They both resonate," explains aerospace engineer Rodney Rocha of NASA's Johnson Space Center (JSC) in Houston.

Credit: NASA

"When you pick up an acoustic guitar," Black demonstrates, "one of the first things you'll notice is the body is basically an air chamber. The shape of the chamber is designed to be 'in tune' with the sound from the strings." He plucks the E string and the body of the guitar vibrates, producing "sympathetic" E-frequencies of its own.

"We call this 'resonance' and it's a big part of what makes a great guitar," says Black.

Resonance may be great for guitars, but "it can be disastrous for a spacecraft," notes Rocha.

"When the shuttle lifts off, the main engines roar so loudly that a person standing near the pad would be killed—not by the heat of the exhaust, but by the sound of the engines," he says. The engines "strum" the spacecraft with incredible force. Rumbling sound waves penetrate the shuttle and its cargo, seeking, probing, shaking.

"We cannot let these sounds [find] and over-excite a sympathetic resonance," says Rocha. If they do ... the sound is amplified, vibrations increase. Bolts can become unscrewed, covers ripped off, joints loosened.

"It could really shake up your mission," laughs Black.

The engines aren't the only source of sound. After liftoff, the rocket rips its way through the atmosphere en route to space. Rushing air creates strong aerodynamic noise, which rattles the ship. "You can hear this kind of noise by rolling down your car window while driving," Rocha says.

Even in space, the noises don't stop. Vibrations can ripple through a spaceship when it docks with another ship, or when it fires its maneuvering thrusters. With each bump or thrust, the rocket is strummed anew.

Part 2

When Black strums his guitar, the sound lasts a long time. "That's the sustain," he explains. Long-lasting vibrations are encouraged by the fabric of the guitar itself. "Notice how the guitar is made of lightweight, flexible wood—a material that likes to vibrate," points out Black.

Rockets are made of stiffer, heavier materials, that damp resonances and reduce sustain. But that's not the only trick spacecraft designers use. Sometimes they modify the shape of the rocket, adding supports or filling in empty spots. The purpose: to detune the rocket from itself.

Detuning rockets isn't easy because, as instruments, they're much more complicated than guitars.

Consider this: A guitar is constructed from dozens of parts: tuning knobs, clamps, the sides and faces of the air chamber and, typically, six strings. The strings produce six fundamental frequencies: 82 Hz, 110 Hz, 147 Hz, 196 Hz, 247 Hz, 330 Hz corresponding to the open notes of E2, A2, D3, G3, B3, and E4.

A typical rocket, on the other hand, is made of thousands of parts. The space shuttle famously contains more than a million components. All these pieces vibrating together produce a cacophony of frequencies ranging from subsonic waves that only an elephant could hear to high-pitched whines akin to fingers scratching a blackboard.

Which frequencies might do the most damage? What parts of the spacecraft are most vulnerable to resonance? And how do you de-tune this complicated instrument?

To answer these questions, NASA engineers have developed "sound studios" for spacecraft. "These are huge chambers where we take pieces of our rockets and expose them to loud noises." Really loud. "One of our 165 decibel acoustic horns at JSC can make as much noise as a space shuttle main engine," he says.

By observing the response of "test articles" to the sounds, engineers can discover resonances and make changes to squelch them. "The most vulnerable articles tend to have low mass and lots of surface area—like a guitar," he notes.

Acoustic testing has been a regular part of rocket design since the Apollo program four decades ago. "In those days," says Rocha, "NASA engineers blasted sections of Saturn rockets with loud sounds in special laboratories. And when the space shuttle came along we tested its components in the same way."

Now NASA is preparing to build a new spaceship, the Crew Exploration Vehicle (CEV) to carry astronauts back to the Moon and on to Mars. "I'm sure the CEV will get its turn in a sound chamber, too," says Rocha.

aussiergman- Egg Boxes work as great sound proofing - went into a music shop once with it - the sounds were deafening inside but you couldn't hear a thing outside - I had to go in and out a few times to believe my ears

Hey T2J, just thought i'd share the press release for the new Sherrie Lea cd with y'all :o)

***FOR IMMEDIATE RELEASE***

SHERRIE LEA FULL LENGTH ALBUM “SPELLBOUND” OUT NOW!!

Talented Canadian artist Sherrie Lea’s full-length album, “Spellbound” out today on Hi-Bias Records (Distributed by Warner Music Canada)

Sherrie is one of Canada’s top female vocalists, having been featured on the best selling compilations “Women In Song” alongside the likes of Sarah McLaughlan and Nelly Furtado. Her first single, a reworking of the Sade hit “No Ordinary Love”, was an international smash, and performed extremely well across Canada, garnering one thousand spins at CHUM FM and Z103.5 FM radio alone, as well as charting top ten in the club charts. On the strength of the single alone, Sherrie was offered an international signings in the UK, Scandinavia, Spain, France, and more. Her second single and title track “Spellbound” is currently charting as the #8 radio pick hit and is the #2 hot most added track at HOT AC radio.

“Spellbound” is an exhilarating musical ride, with dance floor and radio friendly sounds as the cornerstone. Exciting, upbeat, and deliciously sultry, Spellbound contains exclusive co-writes by Bryan Adams and Alanis Morissette as Sherrie Lea wraps her signature voice around undeniably catchy melodies, and lyrics that are simply, unforgettable. Produced by ace remixer/producer Nick Fiorucci (Britney Spears, Celine Dion, Laura Pausini, etc), “Spellbound” is an unquestionable groover that is bound to be a hit!

Please feel free to visit www.sherrielea.com for more artist information and a link to the video for “No Ordinary Love”.

For press inquiries, additional artist information, live appearances, etc. please contact info@hibias.ca

962..thank you for the positive review...it does my heart good. The butterfly sounds you described on "Jimi's Amoung Us" is 1 guitar, 1 take through an Eventide Eclipse Harmonizer ... very cool unit...

Thank you for taking the time to listen, and responding in detail...I've been thinking of shopping my tunes for soundtracks, or commercials within the next year or so once I've built a substancial catalog of work...time, time, time...tick, tock, tick, tock....

danny k...are you on the CD...congrats & cheers!

hey there Joe how are you today buddy? I am doing ok. A lot better than yesterday. Well except I went snowboarding yesterday. Have a great day. lots of love.

How is every one today?

have a great day!

Not to sound weird or anything but man i just now called freinds my most favorite song of all time!!! its wonderful melodic and sweet sound gives it a real "happy" personality. everyone of your (satch) songs have sooooo much emotion but i think this song is heavenly!!!! i play in a band with a bunch of 80's metal heads (and im one as well) and i got them to listen to you and they just love you. i think everyone in the world would like atleast one of your songs. anyway when we practice we warm up by just jamming and ill solo to what ever the rest of the guys are doing. but ill tell you this. even thouh they like you they hate it when i solo in a happy mode (i play ionian alot) because im a happy guy and i also TRY to play some of your solos but the happiness just kills my freinds but thats who i am i guess!!

Danny K...... That's great news. I'm really happy for you. Any chance of you playing Chicago in the future?

Zen and other dudes - what the T2J Symphony all about then??

I just pretend to be so that everyone will like me... lmao..

what did you listen to..???

much better than IUMA.. that place stank...

Listening to "Motorcycle Driver".....great tune !

Stevee T, nice man, I didn't figure that track to be one guitar through an Eventide, but it all makes sense now! God I love Eventide stuff, I'd love to get one of their harmonisers to play with! And hey that's cool that you're thinking of "shopping your stuff out" for soundtrack purposes. Keep us posted!

And if you want to go into loads of detail, angle the mesh on the front of the cab back by about 5 degrees! hehe. It's looking sweet though dude, I'm in awe at your skills, I wish I understood 3D modelling and rendering!

hey guys, this might be the answer, for us guitarists who like to record there amps at 10 , portable sound bootth if u do something like that, what sort of mic would be good to use ? sure 57 i think is one I know of , any others? cause I realize now , that the sound of the amp is different thru the speakers than going from the send returns or line out, and I wanna get the reall warmth sound that i get thru the speakers...

I'm learning all of Joe's songs in the "best of Joe Satriani" book. The legato lick at the start is really tiring :(