What's the science of sound?

Understanding sound waves, sonic booms,
and the speed of sound are key to understanding how X-59 will quiet the boom.

The Physics of Waves

Waves are created when energy is transferred through a medium like water or air. There are two types of waves, transverse and longitudinal (sometimes called pressure or compression waves).

When people think of waves, they often think of transverse waves.
Click each video to see an example and explanation of both types.

Longitudinal Waves

Transverse Waves

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Sound waves and units of measurement

Sound waves are longitudinal waves that travel through a medium like air or water.

When we think about sound, we often think about how loud it is (amplitude, or intensity) and its pitch (frequency).

Artist illustration of modication 3 of the X-57.

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The speed of sound

Diagram showing the speed of sound. Speed of sound (a) depends on the type of medium (e.g. air, liquid, solid) and the temperature of the medium. a=sqrt (Y R T). Y = ratio of specific heats (1.4 for air at STP); R = gas constant (286 m2/s2/K for air; T = absolute temperature (273.15 + °C)
Graphic showing how Mach is calculated. The X-59 will fly at Mach 1.4. Ratio = Object Speed divided by Speed of Sound = Mach Number. Subsonic Mach < 1.0; Transonic Mach = 1.0; Supersonic Mach = > 1.0; Hypersonic Mach = 5.0
Graphic showing how Mach is calculated. The X-59 will fly at Mach 1.4. Ratio = Object Speed divided by Speed of Sound = Mach Number. Subsonic Mach < 1.0; Transonic Mach = 1.0; Supersonic Mach = > 1.0; Hypersonic Mach = 5.0

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Sonic booms

When an airplane flies at or above the speed of sound,
air molecules cannot move out of the way of the airplane fast enough, so the pressure waves combine to generate a large shockwave, which people on the ground hear as a sonic boom.

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Quieting the boom

At NASA, we’ve done 70 years of supersonic research to help us understand and eventually quiet the boom!

Christine Darden, one of the original 'hidden figures' of NASA, who went on to do years of sonic boom research at NASA's Langley Research Center in Virginia
Graphic showing how Mach is calculated. The X-59 will fly at Mach 1.4. Ratio = Object Speed divided by Speed of Sound = Mach Number. Subsonic Mach < 1.0; Transonic Mach = 1.0; Supersonic Mach = > 1.0; Hypersonic Mach = 5.0
Graphic showing how Mach is calculated. The X-59 will fly at Mach 1.4. Ratio = Object Speed divided by Speed of Sound = Mach Number. Subsonic Mach < 1.0; Transonic Mach = 1.0; Supersonic Mach = > 1.0; Hypersonic Mach = 5.0