# Subsonic vs. Supersonic — What's the Difference?

By Tayyaba Rehman — Updated on September 28, 2023
"Subsonic" refers to speeds below the speed of sound, while "Supersonic" denotes speeds exceeding the speed of sound.

## Key Differences

"Subsonic" and "Supersonic" are terms used in aerodynamics to describe velocities concerning the speed of sound. When something travels at a "Subsonic" speed, it moves slower than the sound waves it generates. This results in sound waves moving ahead of the object, ensuring that one can hear an approaching "Subsonic" object before seeing it.
Tayyaba Rehman
Sep 28, 2023
"Supersonic," on the contrary, describes velocities that surpass the speed of sound. An object moving at a "Supersonic" speed will outpace the sound waves it produces. The compression of these waves is responsible for the sonic boom often associated with "Supersonic" speeds. Consequently, a "Supersonic" jet will pass by before its sound reaches an observer on the ground.
Tayyaba Rehman
Sep 28, 2023
It's essential to understand the significance of the speed of sound in these definitions. In standard atmospheric conditions at sea level, the speed of sound is about 343 meters per second (1,125 feet per second). If an object's speed remains below this threshold, it is "Subsonic." If it exceeds this value, it's "Supersonic."
Tayyaba Rehman
Sep 28, 2023
To delve deeper, aircraft and other objects can experience both "Subsonic" and "Supersonic" conditions. For instance, during acceleration, an aircraft might transition from "Subsonic" to "Supersonic" speeds, breaking the sound barrier in the process.
Tayyaba Rehman
Sep 28, 2023

## Comparison Chart

### Speed Relative to Sound

Below the speed of sound.
Above the speed of sound.
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Sep 28, 2023

### Sound Waves

Lag behind the object.
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### Audibility

Object's sound heard before it's seen.
Object seen before its sound is heard.
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### Associated Phenomenon

No distinct sonic occurrence.
Produces a sonic boom.
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### Typical Usage

Commercial air travel, general aviation.
Military jets, experimental aircraft.
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## Compare with Definitions

#### Subsonic

Pertaining to velocities slower than sound waves.
The drone's subsonic motor was almost silent.
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Sep 28, 2023

#### Supersonic

Denoting motion where the object precedes its sound.
The supersonic jet was visible long before its roar was heard.
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Sep 28, 2023

#### Subsonic

Denoting motion where sound precedes the object.
The subsonic car's engine roar was heard before it appeared on the horizon.
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#### Supersonic

Speeds surpassing the speed of sound.
The fighter jet can reach supersonic speeds.
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#### Subsonic

Relative to conditions or movements below sound speed.
Subsonic wind tunnels are used for specific aerodynamic testing.
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#### Supersonic

Characterized by exceeding the threshold of audible sound speed.
The aircraft's supersonic flight caused a loud sonic boom.
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#### Subsonic

Speeds less than the speed of sound.
Most commercial airliners operate at subsonic speeds.
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Sep 28, 2023

#### Supersonic

Pertaining to velocities faster than sound waves.
The missile traveled at supersonic speeds to its target.
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Sep 28, 2023

#### Subsonic

Characterized by being under the threshold of audible sound speed.
Subsonic ammunition is favored for its reduced noise.
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Sep 28, 2023

#### Supersonic

Relative to conditions or movements above sound speed.
Supersonic aerodynamics is a specialized field of study.
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#### Subsonic

Relating to or flying at a speed or speeds less than that of sound
Subsonic aircraft
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#### Supersonic

Involving or denoting a speed greater than that of sound
The tip speed of the upwind blade becomes supersonic
Supersonic aircraft
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#### Subsonic

Of less than audible frequency.
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#### Supersonic

Having, caused by, or relating to a speed greater than the speed of sound in a given medium, especially air.
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#### Subsonic

Having a speed less than that of sound in a designated medium.
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#### Supersonic

Of or relating to sound waves with a frequency above the range audible to the human ear; ultrasonic.
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#### Subsonic

(of a sound, scientific) having a frequency too low to be audible
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#### Supersonic

(of a speed) Greater than the speed of sound (in the same medium, and at the same temperature and pressure).
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#### Subsonic

(of a sound, literary) very quiet, almost inaudible
The noise of the ship was all around her. The faint subsonic rumble of the reactor and drive. (Leviathan Wakes, James S. A. Corey)
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#### Supersonic

Ultrasonic, having a frequency too high to be audible.
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#### Subsonic

(of a speed) (aviation) less than the speed of sound (in the same medium, and at the same temperature and pressure)
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#### Supersonic

An aircraft that can travel at the speed of sound.
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#### Subsonic

With a Mach number such that 0.3 < Ma < 0.8 (approximately - the exact limits vary between sources)
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#### Supersonic

Moving at a speed greater than the speed of sound in air; - this speed varies with altitude, since the speed of sound varies with altitude, as well as with temperature and humidity, being approximately 1129 feet per second at sea level and 984 feet per second at 16 miles altitude.
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#### Subsonic

An aircraft whose maximum speed is less than the speed of sound
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#### Supersonic

Capable of moving at speeds higher than the speed of sound; - of aircraft.
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#### Subsonic

(of speed) less than that of sound in a designated medium;
Aircraft flying at subsonic speeds
A supersonic bomber flies so fast that it must release its bombs while the target is still over the horizon
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#### Supersonic

(of speed) greater than the speed of sound in a given medium (especially air);
A supersonic bomber flies so fast that it must release its bombs while the target is still over the horizon
Aircraft flying at subsonic speeds
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#### Supersonic

Having frequencies above those of audible sound
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## Common Curiosities

#### What causes a sonic boom?

It's caused by the compression of sound waves when an object moves at "Supersonic" speeds.
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#### Is "Subsonic" always silent?

No, "Subsonic" simply means the speed is below the sound barrier. Sound can still be produced.
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#### What's the main difference between "Subsonic" and "Supersonic"?

"Subsonic" is below the speed of sound; "Supersonic" is above it.
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Sep 28, 2023

#### Can a plane transition from "Subsonic" to "Supersonic" speeds?

Yes, certain aircraft can accelerate past the sound barrier, transitioning from "Subsonic" to "Supersonic."
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#### Why don't commercial flights go "Supersonic"?

Noise concerns, fuel efficiency, and cost make "Subsonic" speeds preferable for commercial aviation.
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#### Can sounds be "Supersonic"?

No, sounds travel at the speed of sound. Objects or waves can move "Supersonically" relative to the medium they're in.
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#### Are all military jets "Supersonic"?

Not all, but many are designed to achieve "Supersonic" speeds for various mission requirements.
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Sep 28, 2023

#### Is breaking the sound barrier dangerous?

It can be for unprepared structures, but modern aircraft are designed to handle "Supersonic" transitions safely.
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Sep 28, 2023

#### Are there speeds faster than "Supersonic"?

Yes, "Hypersonic" refers to speeds much greater than the speed of sound, typically over Mach 5.
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Sep 28, 2023

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