What causes background hiss or static?

F

fuzzybabybunny

Active member
Sorry, I know that this must be a very basic question. I was looking at video reviews of wireless bluetooth audio microphone systems. The UHF ones are all too big and bulky for me, and this Sony bluetooth one is tiny in comparison:

https://www.youtube.com/watch?v=Dahx57qXVSM

The form factor is amazing, BUT:

- I notice a constant background hiss. What could cause this?
- Is this normal? Is it something that has to always be removed in post?

I've noticed this background hiss before when I plug my headphones into a cheap audio source, and I can remove it by adding a Ground Loop Noise Isolator.

https://www.amazon.com/dp/B06XQYN77...od-20&creative=395033&creativeASIN=B06XQYN77L

The big downside to using one of these is that the volume level drops quite a bit. If I can normally listen to music at volume level 5 out of 10, I have to crank it up to 8 or 9 out of 10 when using the ground loop isolator.
 
IronFilm said:
It is low quality crap, that is why. Don't get bluetooth wireless for production audio, I'd suggest at a minimum get a Sony UWP-D11 set.
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That's not a very technical answer. What exactly is causing it? Because other video reviews of the same mic don't exhibit it.
 
He's using a GH4 to record and mentioned that he bumped the levels up in the camera...and that's what introduced the hiss/static.

The internal preamplifiers in those kind of cameras are noisy and that's what you hear.

The mic isn't the issue...but it's a lose-lose situation as the electronics in this Sony system are subpar, so you'll have to keep the 'volume' down but then raise your levels in your camera, or lower them there and raise the Sonys.

The only ideal scenario for this system (without anything else) is using a camera with very good preamps and a very sensitive mic that doesn't need much boosting.

People definitely also clean up the hiss in post.

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P.S. Many who choose to record audio into their camera use external preamps.

A device such as the one below for the GH4 and other similar cameras would allow you to keep the levels inside the camera at an absolute minimum while providing you a strong signal thus eliminating any if not all of the hiss/static.

There are other options too: https://www.bhphotovideo.com/c/prod...cro_pro_dxa_micro_pro_active_xlr_compact.html

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P.P.S. I can't explain why this happens like maybe a sound engineer could, but that is the answer in layman's terms.

Cheap electronics = weak signal.

You try to raise levels to get a strong signal = hiss/static sound.

Solution: Use better hardware to help you get a strong signal while keeping in-camera levels down while eliminating hiss/static sound.
 
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NorBro said:
The mic isn't the issue...
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Disagree. Those little bluetooth systema have cheap components of their own, and have their own, noticeable noise floor. Add to that cheap companding and the noise floor is amplified. Add to that what you mention about noisy DSLR pre-amps and it's an all-around bad situation.
 
Alex H. said:
Disagree. Those little bluetooth systema have cheap components of their own, and have their own, noticeable noise floor. Add to that cheap companding and the noise floor is amplified. Add to that what you mention about noisy DSLR pre-amps and it's an all-around bad situation.
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I hear you...but just wondering if you watched the entire video?

He started the test with the built-in microphone on the device, which is of course not good, and then plugged in the Sennheiser ME2 to test.

I don't think it's the microphone's fault when you're using it with such hardware and essentially setting it up to fail.
 
One of the cheapest but usable wireless systems is the Azden PRO XD unit that costs about $200 US, but you have to replace the horrible LAV mic that comes with it. ( I would replace the LAV with an Oscar SoundTech OST-801 or OST-802 lav, that costs about $90 )

Make sure you check out the end of this video where Curtis replaces the horrible LAV that comes with the system...

 
There are quite a few things that could be contributing to the noise including post issues. Which is why it's just plain silly to try and judge how anything sounds in a YouTube video. Though an A/B comparison has some possibly useful info. The problem is you have no idea how apples to apples these comparisons are.

But BlueTooth has issues and I wouldn't use it for anything important. All BT devices I have ever owned have periodic connection issues and have to reconnect. Killer for production. This has tiny electronics that are really consumer grade which means they have more internal noise than better parts. The whole chain in the video is a bit weak from a sound perspective so the noise is probably a bit from all of them, but the BT is the weakest link and is probably where much of the noise is coming from.

As to fixing in post. Yes and no. Yes electronic hiss is generally easier than most noise to get rid of but... It's a subtractive process so you are always going to loose some of what you want along with what you don't. Plus you have a workflow issue. When do you do the cleanup? Each take is going to be slightly different (probably) in terms of noise so you want to take noise prints and do NR on each clip individually. So do you do it on all clips before you edit? That could be a lot of wasted time working on takes you don't use. If you wait till after the edit then you have a lot of cuts and so now you are dealing with doing sub-clips and that can be VERY time consuming.

Some times you can cheat a bit and if it's all really similar you may even get away with a track plugin and just do it on the fly. But as a rule that is not a good practice except with either a very light pass or ENG kinds of stuff where you are cranking out "good enough" because you are on deadline.

So yes you could probably do a pretty good clean up on this BUT a short film might take a weak of just NR to do it right.
 
Are there any ultra-compact travel setups that don't require any kind of post-processing to remove background hiss?

I have a cheap (but highly reviewed) Purple Panda lav mic. The background noise is bad when recording into my laptop. It's even worse when recording into my Microsoft Surface tablet. Background hiss is lowest on my Samsung S5 phone, weirdly enough.

- Would recording directly into a Zoom H1n be much better?

- Is the noise introduced predominantly by a low quality preamp?

- Is there a wireless system that is mostly digital and only does one conversion from analog to digital?

As in:
Analog mic-level signal from the microphone gets converted to digital in the transmitter (By going through the preamp and then the A/D converter in the transmitter. Once it's in digital form, it should be much less susceptible to outside noise when transferred around).
Digital signal gets wirelessly transmitted to the receiver.
The receiver sends the digital signal via USB to a recording device.
The digital signal gets saved.

- With traditional methods, the analog and digital signals get converted back and forth all over the place.
In the case of a corded mic:
Analog mic-level (millivolt) signals from the microphone has to travel through lengths of heavily shielded high quality cable. If not heavily shielded or balanced, lots of noise can be introduced.
The preamp amplifies this weak signal, which might have picked up additional noise along the way.
The A/D converter than converts a possibly compromised analog signal into digital, to be saved on the recording device.

In the case of the bluetooth system:
Analog mic-level signal from the microphone gets converted to digital inside of the bluetooth transmitter's preamp and A/D converter.
Digital signal travels from the bluetooth transmitter to the receiver.
The receiver runs the digital signal through a D/A converter, and brings the signal down to mic-level.
The mic-level analog signal gets sent to the phone/camera/recording device's 3.5mm analog mic jack.
The recording device's preamp amplifies this mic-level signal and runs it through it's own A/D converter.

Both the analog wire and wireless bluetooth systems have way more points where noise can be introduced.
 
laptops are notoriously noisy on their mic ins. And yes it's probably cheap electronics. That mic in was to give the thing voice commands or make phone calls not record decent sound. The phone makes sense since it is made for capturing voice.

On top of the general low quality that is likely in BlueTooth it is also relatively low bandwith so I would not be surprised if it's compressing the signal to lower the data rate. That could also add to the "noise".

There are ultra compact transmitters that are good but they are $$$$ I think Zaxcom makes a really small digital transmitter.
 
fuzzybabybunny said:
I was looking at video reviews of wireless bluetooth audio microphone systems. The UHF ones are all too big and bulky for me, and this Sony bluetooth one is tiny in comparison:

https://www.youtube.com/watch?v=Dahx57qXVSM

The form factor is amazing, BUT:

- I notice a constant background hiss. What could cause this?
- Is this normal? Is it something that has to always be removed in post?
Click to expand...

Here's the problem of trying to cheap out with audio. Cheap mics tend to be not very sensitive. To get their levels up to a usable point, they need lots of clean gain from the mic preamps. This flies in the face of cheap mic preamps (in particular, mic preamps in a camera), which have very little clean gain available; they demand a strong signal from the mic, which your cheap mic can't deliver. The combination of cheap mics with cheap micpres gives you noise. No way around that.

As to blue tooth... it's acceptable for use with phone headsets, but not a lot else. Using it to record dialog audio is just beggin' for trouble. And blue tooth will oblige you. The connection issues alone will drive you bonkers.

Wireless in general is way over used. Wireless is a last resort. Not first. Last. No, I'm not kidding. A $20 USD 5m XLR cable is orders of magnitude less expensive, orders of magnitude more reliable, and sounds better than even the best wireless systems. Always use a cable if you can. Always.
 
Noiz2 said:
laptops are notoriously noisy on their mic ins. And yes it's probably cheap electronics. That mic in was to give the thing voice commands or make phone calls not record decent sound. The phone makes sense since it is made for capturing voice.

On top of the general low quality that is likely in BlueTooth it is also relatively low bandwith so I would not be surprised if it's compressing the signal to lower the data rate. That could also add to the "noise".

There are ultra compact transmitters that are good but they are $$$$ I think Zaxcom makes a really small digital transmitter.
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I don't think Bluetooth is that bad for audio. AptX and AptX Low Latency produce very acceptable audio quality. Having used AptX Low Latency on headphones, the lag is almost imperceptible and the sound quality is very good. AptX HD is probably going to be even better. HFP is pretty bad, but that's old tech.

Compression by itself isn't that big of a deal. The difference between a 320kbps mp3 and flac file is hardly ever noticeable, so the compression itself can still result in high quality. The time required to compress, encode, and decode can add lag if recorded on the same device as the video is, but it should just require a quick shift of the audio track in post to fix.

The real killer is all the back and forth between analog and digital and trying to transmit analog signals over distance.
 
I don't think Bluetooth is that bad for audio. AptX and AptX Low Latency produce very acceptable audio quality. Having used AptX Low Latency on headphones, the lag is almost imperceptible and the sound quality is very good. AptX HD is probably going to be even better. HFP is pretty bad, but that's old tech.
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Consumer headphones VS production sound... The bar is (or should be) in a very different place. For one thing listening isn't recording. Your brain can mask small glitches, especially if it's music you know.
This is actually one of the biggest hurtles for people starting to record. It takes some time before you learn to turn off your brains "auto correct" and really listen to everything.

Compression by itself isn't that big of a deal. The difference between a 320kbps mp3 and flac file is hardly ever noticeable, so the compression itself can still result in high quality.
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On one level I agree, but only as a delivery format. The fly in your ointment is that, that MP3 only has 10% or so of the data of a WAV file. It is a very smart 10% so you don't really hear it but when you start doing post on it it will fall apart quickly so it's a bad choice for acquisition. But I was mentioning it as a possible source of the noise. It's not the compression per-say but the compressing and uncompressing that can add noise.

The time required to compress, encode, and decode can add lag if recorded on the same device as the video is, but it should just require a quick shift of the audio track in post to fix.
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Two problems. First anything that contains "in post to fix" is a bad way to start. "Fixing in post" should be only for the oopses that nobody thought of in production. Second it's not "quick" for the reasons I pointed out with NR. All of the devices that have had noticeable lag (in consumer wireless/ BT etc.) that I have played with have that lag vary depending on congestion and distance.

A possible exception to the above would be an in sync guide track and using something like PluraEyes to sync your lagged audio. Since it does a clip by clip sync it sould do a pretty good job of dealing with variable lags and it is pretty quick. Plus with dual system you have to sync anyway.

The real killer is all the back and forth between analog and digital and trying to transmit analog signals over distance.
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;~)... since we are talking about a digital wireless system here that would kind of be the point no?
 
Anything that amplifies audio or processes audio in any way has what's called "self noise". That means these things will generate some level of noise, which sounds like hiss. The better the components, the lower that level is. Really cheap components made en masse with low quality control tend to get used in lower cost wireless systems, mics, recorders, mixers...and so on. The reason professional gear is expensive is because the best components and circuits are used/designed to get the lowest level of self noise possible. This means they typically don't use off the shelf circuit boards and whatnot. Something like a Sound Devices 633 or 744t was engineered and designed by the factory and had those boards built especially for them..down to the mic pres and and A/D converters. Other low cost gear just uses off the shelf pres and A/D converters. They are usually OK, but don't perform as well as the high end stuff. Camera and phone manufacturers are usually looking for the cheapest audio components they can find because they are more concerned about the image than anything else. I really don't like relying on them as my primary audio recording medium.

The takeaway here is if you try and do audio on the cheap, don't expect big budget film results. This may be fine for youtube style videos or for web streaming, but it might not be okay for narrative or reality work.
 
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