# Has sound ever been used to diagnose a problem not shown by other measurements?

In a video released by NASA here, showing Perseverance recording one of Ingenuity's flights, they have the quotes:

Sound adds a new dimension to space exploration.

and

As a mechanic listens to a car, engineers can now hear how their machinery is performing on another planet.

I'm curious at to whether there have been any documented issues solved by an engineer or astronaut hearing something out of place.

While I'm mainly looking for humans diagnosing an issue based on sound, we already know that acoustic triangulation has been used to determine failure within a rocket:

"We’ve got microphones, technically accelerometers, at various points on the upper stage, and by looking at the exact timing of high-frequency events on the stage, we can, by acoustic triangulation, identify the location where the snap occurred or the breakage occurred via sound." - Elon Musk

So any examples of automated acoustic diagnosis would also be interesting.

• I think it's common practice in aircraft maintenance to use ultrasound to detect cracks and other defects in steel. This takes specialized equipment beyond just a mic. It probably doesn't pay off to do this in rovers designed to last just a few years, plus it takes trained technicians or robotic replacements to do this, but down the line, once we truly take to space, my guess is very much yes, we'll use similar techniques to identify structural faults that need correcting?
– user39728
May 8 '21 at 4:04
• Ultrasonic inspection doesn't require atmosphere. I guess the NASA. Musk's quote from the other link "“We’ve got microphones, technically accelerometers," is presumably also about sound transmission through the structure which also has nothing to do with the atmosphere. Continuous monitoring of vibration in operating machinery with accelerometers is nothing new. For example internal cracks developing inside jet engine fan blades (and many other possible failure mechanisms) can be detected from changes in the vibration spectrum while the aircraft is operating, without manual inspection. May 8 '21 at 15:07
• mentalfloss.com/article/24107/space-can-anyone-hear-you-scream May 10 '21 at 16:41

The shuttle Orbiter's wing leading edges, constructed of reinforced carbon-carbon (RCC) composite material, were tested in part by technicians tapping on them and listening to the resulting sounds. It didn't work all that well though, and was replaced by infrared thermography.

Sources

I'm not sure how widely you are casting the breadth of your question. But I know jet engine mechanics always listen to a turbine as it runs up, reaches steady state, then is powered down. I knew the chief engineer for Flying Tigers in the 1970s who was a grizzled old guy who put his ear against an engine's nacelle to listen to the bearings and oil pumps. He could diagnose things no one else or any instrument could detect. However, it left him nearly completely deaf by the time he retired. Acoustics are used for non-destructive testing of materials and joints that may have defects that are nearly undetectable by standard x-ray methods. I recall that Apollo and Gemini astronauts commented about whether the booster engines were running smoothly enough as they listened to or felt the vibrations coming into the capsule. Older astronauts sometimes said they used their pilot's experience with sound and vibration in part to know when to punch out -- hit the escape system.

There is another point: detecting the transition from periodic to chaotic motion in a vibrating system of any kind. That transition may be easily detectable in some systems, more subtle or ambiguous in others. But there are plenty of examples when that transition indicates the system is about to malfunction -- or rapidly disassemble. It is sometimes difficult to characterize or model.

• These days, a computer "listens" to such things continuously during flights, and AI systems can predict the likely cause of vibration signature changes and alert the maintenance engineers (and the flight crew, if relevant) of possible problems before the plane has even landed. May 8 '21 at 15:12
• @alephzero do you have a reference? that's very interesting and I'd like to read more. May 8 '21 at 18:57

### If you count ultrasound inside metal as sound:

After some research and this article I found out that they are using a system called Distributed Impact Detection System (short DIDS) to detect these impacts. NASA describes the system like:

DIDS units are high-speed, four-channel digitizers that record ultrasonic noises. Instead of listening for the hiss of air, these units detect the high-frequency sounds moving through the metal itself

There are a few of these systems installed in different modules at the ISS

Detailed information about the system can be found in this technical report of NASA Distributed Impact Detector System (DIDS) Health Monitoring System Evaluation.

### If you count ultrasound

Several leaks aboard the ISS were first discovered by an increase in the rate of depressurization of the station that could not be accounted for by known causes. These can be localized to "which compartment?" by closing various hatches and monitoring the pressure drops in them.

However before you can FIX the darned leak, you need to find and identify it exactly.

Ultrasound is used to find leaks that are not egregious enough to make a whistling sound we can hear with our ears.

The video below, found in Spaceflight Insider's How was the exact location of the recent ISS air leak found? shows clips of use of an ultrasonic leak detector aboard the ISS and at least one instance where it seems a leak was repaired.

After astronauts determined from which of the modules the leak is coming from, in this case the upper section of the Soyuz MS-09 spacecraft, they used a device called an ultrasonic leak detector (ULD) to find the precise location of the Soyuz spacecraft that was leaking atmosphere.

below: screenshot from a recent Roscosmos tweet of cosmonaut Sergey Prokopyev(presumably) talking about the lead detection and repair and showing an ULD? (I can't speak Russian, but presumably this is correct.) Translating the text using Google:

"Friends, I decided to shoot a video to answer your numerous comments and dispel rumors. Everything is calm on the ISS! "

• The tweet video indeed said that after the procedure to determine which module is leaking, they "used this ultrasound sensitive device" which led them to a 2mm hole behind a cover. May 9 '21 at 18:06
• @BeniCherniavsky-Paskin that's great to know, thanks! If you would like to add a translation of part of it to this post please feel free to make an edit! If you would like to do that as a separate answer here, that's great also! I'm sure there is more information available in Russian that you could add to it.
– uhoh
May 9 '21 at 18:19

### If you count seismic vibrations as sound

The SEIS team had this to say in Review of the commissioning phase of the SEIS seismometer on Mars.

During the same period as the calibration operations, the SEIS seismometer also began listening to the vibrations caused by the HP³ mole as it headed down through the Martian sub-soil during sols 92 and 94.

The data collected showed that the SP sensors of the SEIS seismometer, well-suited to high-frequency measurements, record a variety of information—not only on the penetration operations but also on the mole’s internal operation. The signals are so strong when the mole begins hammering that the VBB pendulums saturate.

The objective of the SP sensors is to determine as accurately as possible the arrival time of the signals generated by the complex movements of the mole’s various moving parts whenever it hammers to move forward. A dedicated digital filter will be uploaded to the eBOX electronics unit that controls SEIS to increase the temporal resolution. Depending what the SP sensors hear, the project engineers will know whether the mole is continuing its downward journey (even slowly), if it is just bouncing off something in its path, or if it is completely blocked.

A second digital filter will also be activated to prevent the seismometer’s ultrasensitive VBB sensors from saturating when HP3 uses its hammering mechanism. By analysing the difference in seismic wave propagation depending on the materials encountered, it may be possible to identify the presence of a very hard layer some 30 cm deep.

• Well actually seismic waves are sound waves, which are really just pressure waves in matter.
– user39728
May 8 '21 at 4:15

It's not a spacecraft (or even an aircraft), but how about finding a bad clamp in a fusion reactor? The Joint European Torus at Culham Centre for Fusion Energy has microphones in the reactor room feeding speakers in the control room, so that the operators can listen for anomalies while it's running.

According to David Homfray, Engineer in charge,

A couple of years ago, we had a disruption and we could hear this clanging noise. And we were able to pinpoint the exact area, and what we believed it was, which was a clamp which held a pipe, and we were immediately able to walk into the area, go to where we believed it was, and found it -- and then could replace it.

Source: Help, My Fusion Reactor's Making A Weird Noise (by Tom Scott), at 2:28.

Note: while this obviously isn't a space application, I'd argue it's a very similar diagnostic usage: JET and Perseverance are both experiments where we have little enough experience that we don't necessarily know about all the failure modes we need to watch out for (yet), and so we don't necessarily have appropriate sensors and/or detection logic for. They're both using audio + human hearing as broad-spectrum things-we-didn't-think-of detectors.

• This is space.StackExchange.com. Unfortunately we don't have fusion-powered spacecraft yet. May 8 '21 at 8:43
• @PeterCordes True; I'll add a qualification. But other than that it seems pretty similar to what NASA's doing. May 8 '21 at 9:09
• Since this is Space SE, "...in space" is pretty much always assumed unless otherwise indicated. Since (as far as we know) humans have never put "fusion reactors" in space, and the question asks for what has been done not what could be done, this doesn't really answer the question as asked. If someone asks an SO question with the python3 tag and someone answers "In Java it's easy, we just..." you could almost hear the dvps (down votes per second). :-)
– uhoh
May 8 '21 at 10:34
• Space or not, it's a perfect example of how engineers can hear something being wrong, diagnose it, and locate the cause sometimes. Similar things could happen on the ISS, for instance, where some abnormal sound may point to some specific problem. May 9 '21 at 13:05
• @uhoh I've added some more explanation of why I consider it a very similar diagnostic technique, despite being in an Earthbound experiment. May 10 '21 at 3:50

Adapted/modified from Microphones on the Perseverance Rover

### Perseverance Has Two Microphones!

Microphone on SuperCam

SuperCam identifies minerals and rock compositions, and it seeks organic compounds that could be related to past life on Mars. It has a laser that can zap and study areas on a rock as small as the period at the end of this sentence. All from about 20 feet, or 7 meters away. Its camera and spectrometers then examine the rock's chemistry. The microphone on SuperCam gives scientists another "sense" with which to probe the rock targets they are studying.

Main Job: To help study Mars rocks

Location:On a short 15 mm boom on the head of the rover’s long mast

Listening when: when the SuperCam instrument is on, for a few milliseconds at a time. Or to listen to wind and for rover sounds for about 3.5 minutes at a time.

What it can hear: the staccato pop caused when the laser studies rock, wind, and rover noises

Hearing the Sounds of a Laser Firing:

When SuperCam fires a laser at a rock, a small amount of the rock vaporizes into a hot gas called "plasma", and heat and vibration creates a shockwave that makes a popping sound. SuperCam’s camera and spectrometer can "read" the hot gas to reveal the chemical makeup of the vaporized rock. At the same time, the microphone hears the staccato "pop" as the laser strikes rock several feet away from Perseverance.

The kind of "pop" it makes tells scientists about the mass and makeup of the rock. The intensity of the sound reveals the relative hardness of the rocks, which can tell us more about their geological context. For example, the hardness of the rock can help tell us whether the rock was formed in a lake or from wind-driven material, or how much pressure was involved in its formation. All without ever driving up and touching it.

SuperCam can listen for about 3.5 minutes at a time while performing science observations. This gives the rover the chance to hear the sounds of Mars, such as the high-pitched sound of sand grains over the surface, the wind whistling around the rover mast, and low-pitched howls of dust devils passing by. The microphone also records sounds of Perseverance using its arm, coring rocks, and the wheels crunching against the surface. The rover may hear the other instruments, internal mechanisms, and hear when we drop off the sample tubes. In some cases, sound can help the team diagnose the health of the rover's internal mechanisms or instruments.

Microphone to Record the Rover's Landing

Main Job: To record the sounds of landing

Recording the sounds of descent, friction from the atmosphere, dust blown up by the thrusters as the rover descends.

Hearing the Sounds of the Rover

Engineers are optimizing this microphone for space from easily available, store-bought hardware. It is unlikely it will work beyond landing. If it does survive, we may be able to hear the sounds of the Martian winds and sounds of the working rover, such as the wheels turning, or the motors that turn its head, and the heat pumps that keep it warm.

### Laser Snap! (not Pew)

The SuperCam mic recorded audio of the Martian wind during Perseverance's first few days on Mars, the instrument team announced today. The microphone also captured the countless rapid-fire snaps of the Máaz work, which came from shock waves generated by the heat and vibration of the rock vaporization.

Such audio will be quite useful to the SuperCam team, Murdoch said. For example, details of the snaps will reveal the hardness of each rock target, a detail that cannot be determined from composition alone. (Chalk and marble have the same chemical composition, as Murdoch pointed out.)

SuperCam recordings will also help the Perseverance team keep tabs on the rover and its various subsystems and allow researchers to better understand the thin, carbon-dioxide dominated Martian atmosphere, Murdoch said.

• This is really interesting, and while not diagnosing a problem, it's great to see how all of the instruments can help each other and provide additional insight (no pun intended). May 9 '21 at 12:22
• @FreddieR I've highlighted "In some cases, sound can help the team diagnose the health of the rover's internal mechanisms or instruments." but ya that only says it can be used, not that it already has been. I don't want to wish that something goes wrong so that they need the microphone to diagnose it, but I'll try to keep an ear out for such an eventuality. For anybody interested: The Mars 2020 Engineering Cameras and Microphone on the Perseverance Rover: A Next-Generation Imaging System for Mars Exploration (singular?)
– uhoh
May 13 '21 at 2:42