why do airline mics sound so bad?
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ELI5: What’s an airline mic?
Not just the mic. Even the inflight audio is bad. Is it to do with the engine noise or pressure. I have noticed that most pilots tend to mumble their sentences which adds to the problem
Because these things are designed solely for reliability and not for your listening pleasure
Depends on which Mic?
The one who hear in the cabin?
These are played out over cheap loudspeakers. There main purpose is to signal an evacuation. They will do this fine when a pilot loudly and clearly calls for it. The chit chat pilots do and all the other attendant announcements are really only a secondary function. As the evacuation announcement is considered safety critical there is a minimum amount of speakers required. So it really is quantity over quality. A typical A320 has 30 rows, a speaker every 3 rows on both sides is around 20 speakers not including the toilets and galleys. To swap them all out to a higher quality one adds up fast.
The ATC mics?
Depends on which radio they are using. Long range ATC comms is done with HF radio which is terrible sound quality. Easily interfered with due to weather etc and is AM modulated so old tech but still has better range then VHF.
VHF is the main ATC comms radio. It is actually pretty clear most of the time and shows the Mics can be pretty good on aircraft. It is affected by reception issues so terrain etc and has a much shorter range that can affect its quality.
Cockpit voice recording mics?
There is usually 4 / 5 mic recordings. One for each radio in the cockpit and one “Area Mic” in the cockpit to record everything. But this is specifically designed to be a wide area mic picking up more sounds but at a lower quality, again designed to be quantity over quality.
With all of the above (except for the area mic) it is usually the same microphone used but the different systems affect its quality in different ways. Modern airline microphones are actually mid to high range mics and not cheap at all. They do get dropped and banged around Alot so they are usually beefed up physically at the cost of some performance but would still be a higher quality of most common consumer microphones.
Aircraft radios are an AM broadcast. AM has poorer sound quality compared with FM, but is cheaper and can be transmitted over long distances. It has a lower bandwidth so it can have more stations available in any frequency range. FM is less prone to interference than AM. However, FM signals are impacted by physical barriers.
Furthermore, the coms are much clearer aircraft to aircraft, I rarely have a problem understanding ATC. If you’re listening to recordings on the ground, that receiver may not be placed in an optimal location, so there will likely be some distortion from ground interference. Much less obstruction from terrain in the air.
If you’re judging based on what it sounds like when the captain talks to the passengers, you cannot make the conclusion that the **Mic** is what’s bad. The **Mic** might be just fine if the passenger cabin **Speakers** are the reason it sounds bad. And those speakers would be the least important thing to make easy to hear. It’s a lot more important for the crew to speak with air traffic control, and with other planes than to speak with the passengers, so it’s entirely possible the passenger cabin speakers aren’t up to the same standard.
Also remember a passenger plane is equipped with several loud white noise generators that never stop called “jet engines”. They’re going to make *every* sound wave that goes through the cabin air harder to distinguish. The white noise is at a high frequency which makes it take mental strain to have your brain’s auditory processing ‘strip’ the noise and pick out the signal.
Meanwhile up in the cockpit, the crew is wearing headsets, not hearing things through the noisy air like the passengers are.
Weight. Dozens of quality speakers weigh quite a bit. Less weight=more profit.
Since lift is a function of thrust and thrust costs money, airlines do everything they can to minimize the amount they need to lift. So the cheap sound of cheap speakers comes from cheap people.
Why should they waste money on audiophile equipment? Sound quality is not a priority for most PA system.
It’s a combination of equipment setup and lack of training.
The headset provides very little side tone when making a PA due to the noise cancellation, so people put their finger over the back of the microphone and pull it close to their mouths. If they’re using the handset to make a PA, they’ll frequently hold it against their lips because they perceive themselves as not being heard.
You’ll get a PA that sounds acceptable by positioning the microphone about 1/2 inch from the corner of your mouth and speaking normally. Anything else sounds like you’re gargling the microphone.
A good airline will train pilots in the correct technique for making good PAs. This costs time, and time = money, so most don’t bother. It does have a noticeable impact on customer satisfaction so it’s worth it in the long run.
Noise-cancelling microphones, which are necessary in a high-noise environment, change the sound of the pilot’s voice. Also, crappy speakers.
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