Q: Can sound travel in space? How do scientists record sounds in space?
Krishna: If space is only vacuum, sound can't travel as sound waves need some medium to travel. The vacuum of outer space has essentially zero air, especially in the vast space between galaxies. Because sound is just vibrating air, space has no air to vibrate and therefore no sound. If you are sitting in a space ship and another space ship explodes, you would hear nothing.
Sound waves are nothing but air vibrations. When these vibrations are in the range of 20 Hz to 20 kHz, we can hear them!
Sound waves basically travel by vibrating the particles in a medium, i.e., molecules of air. These vibrations are passed on to consecutive particles in the medium, meaning that sound waves cannot travel without a medium. The reason we can’t hear sound in the space is typically due to a lack of such a medium.
We may argue that there are clouds of gases in space that can act as mediums, but gases are not present uniformly throughout the space. Moreover, gases are typically less dense in space, which means there is too large of a gap between the particles, so vibrations cannot travel efficiently.
However, according to NASA, it was a popular misconception that "there is no sound in space" because most of space is a vacuum, which leaves no medium for sound waves to travel. The space agency explained that galaxy clusters consist of copious amounts of gas that envelop the hundreds and even thousands of galaxies, thus providing a medium for the sound waves to travel (1,2).
Wherever this medium of gas is available in considerable amount in galaxies, sound can 'exist and propagate' through that medium in space (3)!
Scientists cannot actually ‘hear’ space sounds, but they do have the means to examine the space waves by converting them into sound waves.
Sonification is the conversion of any non-auditory data into sound, and is analogous to data visualization.
A conversion technique is called Sonification if it fulfills certain criteria:
Reproducibility, i.e., important elements of the data remain the same, regardless of the conditions under which the Sonification is done.
The data should be sonified in a way that even untrained listeners can make a distinction.
Space is full ofradio waves,plasma waves,magnetic waves,gravitational wavesandshock waves, all of which can travel in space without a medium. These waves are recorded by instruments that can sense these waves, and the data is transferred to earth-based stations, where the waves are sound coded.
Any audible sound has variables likefrequency,amplitudeandrhythm. Different space waves are matched with different properties of the sound (frequency, amplitude, etc.) in different proportions to get a sound.
Dozens of space sounds have gone through the Sonification process. The human auditory system is unique in the sense that it can identify patterns, so we recognize if a certain tone is repetitive or not. This capability has been used by scientists to segregate and identify data.
Scientists from NASA have recently released an eerie, Hans Zimmer-like audio from a radar that captured sounds from a black hole at the centre of the Perseus galaxy cluster. The actual sound waves were discovered in data collected by NASA's Chandra X-ray observatory and have been converted from astronomical data into human-hearable sound. The release coincides with Black Hole Week.
NASA releases eerie audio recording from black hole
Data Sonification: Black Hole at the Center of the Perseus Galaxy Cluster (X-ray)
This sonification is different from previous efforts that simply translated astronomical data into an auditory form using different instruments. This time, the agency resynthesized the soundwaves to accommodate the human hearing range, scaling them upwards by 57 and 58 octaves above their real pitch. But these sounds were not replayed using violins or other instruments.
You can actually 'listen to' various space sounds here:
