I had an in-person recording for the podcast and a recording with zoom H4N. There is a big zzzzzz through the entire wav. file. Is there anyone that knows?
Here is the link of a short piece of the recording.
https://drive.google.com/file/d/1G1rVk9HEkG4oogdFdRth_P9uTCO8fwBV/view?usp=sharing
…you should be able to directly upload—even just drag-n-drop the wav into your post
It’s something we’re not used to doing but it’s enabled here. Advantage to a purpose built community space 
Need to hear it first - can you adjust the permissions Özlem?
If it is consistent there are some noise removal options
Often a hum like that can be an earth hum - to do with a connection or cables being too close to mics and causing some interference - if we look at the spectrum it might show the most likely culprit.
Have you had this before?
Was the H4N powered via or running on battery?
is there a size limit for adding audio file like this? @craigconstantine
It says ’ new users cannot upload attachments ’
Hi @steveh I adjusted the permission. You will be able to listen to it right now.
Thank you for your feedback.
I already tried:
-Noise Reduction with first noise profile and noise reduction 12 and later 15, but you still hear the zzzzzzz
I haven’t had this before. The sounds was always crystal clear. And the H4N was powered AND running on battery, both at the same time.
oh! I’d forgotten about that. I pushed you up an experience level. Try again.
yeah, there’s a max upload size and there’s a list of permitted file extensions which can be uploaded. I’ve adjusted both here on PodComm.
Oooh! Nasty! Özlem
Playing around with it now - it does sound like an earth loop hum
The spectrum when silent - you can see all of the lines at the bottom (low freq) end - that’s the buzz
Original converted to MP3 from WAV so it will upload
Here is an adjusted version - it is having to take so much noise out it affects the voice a bit too
Here is another version
And then a bit of both RX and Vx
If you wanted to share the whole file, I could run whichever fix you prefer
Do I recognise the voice? It sounds a bit like Lukas from POD
@ozkanozlem
Does Discourse say why you cannot upload it?
Perhaps it’s simply too large? It’s limited to 8Mb… I thought I had made that larger. Would be good to experiment — filesize limits are enforced by both the web server and discourse… so I might have to get the mothership’s help if we go larger and still hit a wall.
Wow! This seems really weird. What do you recommend next time Steve? Only recording with power, taking out batteries? Making sure cables are separate?
Thanks for upgrading me @craigconstantine . I tired to upload the whole episode here, it is 55MB. That seems to be big.
Here is the link @steveh Ozgur Bolat x Ozlem Ozkan.wav - Google Drive It is btw a doctor from Istanbul. He didn’t do POD :).
It is open and you can download it. I am so thankful! But how did you do it? How can I do it next time?
You started by asking the two best questions:
We have found a fix but I am not really sure of the cause so how do you avoid it next time. You need to experiment and try to reproduce the problem - then work out what to change to make the problem go away.
Occasionally connecting to a different power socket is all you need to do but it can be tricky to isolate what the problem is.
You need to know how to avoid it, and then if you can’t, you need to be able to fix it if it happens all the time.
If it only happens occasionally, then you don’t need the expensive software - unless you do, or you want to. You just need to know someone who can fix it for you. This is fairly straightforward and I like a puzzle, so no charge. If it takes a long time I would have to cover my time somehow. We can always talk and keep things clear if you have future problems.
I used:
I’ve had something similar to this in the past.
I had quite long mic cables and found that if I moved them the interference changed, so I’d move them until it stopped. You might find that separating the cables works.
The main thing is listening to the monitor via headphones so that you know it’s good before you start recording.
As a test I tried Descript’s ‘Studio sound’ It was awful and didn’t remove any of the problems, which was surprising as it previously helped a friend’s recording that had loads of mic rustling noise.
Then I tried my favorite ‘hack’ which is Final Cut Pro X video editing software. It did its analysis and added hum removal and noise removal. The hum is gone but there’s still noise I can hear over the voice, so Steve’s work is much better. Or maybe I should just say Steve is much better! 
I tried it too - with the same results. Auphonic, including its beta noise reduction and hum removal, didn’t fix it either. My two-step solution worked by reducing the problem to a lower-level background noise that Clarity Vx could remove. Often it needs multiple layers
It is not perfect but an interesting exercise to try to fix - now to find the cause!
Looking at the frequencies there are strong harmonics of about 50Hz which is the frequency of electrical supply. This suggests it could be connected to the power supply the computer/Zoom H4N was attached too. Alternatively, it could be that the mic or the cables were close to power cords or power supply that picked up the interference.
Test recording plugged into the same power supply or recording using batteries (remember a spare set. And @Mark’s reminder of monitoring by headphones while recording is a strong suggestion to help avoid problems.
Hope it helps you Ozlem and good learning for us all
This was a ‘silent’ piece between speech so it is all buzz and hum.
I tried removing some of the frequencies by hand but it messed with the voices too much
Thank you so much, Steve for this. You can’t imagine how much you helped me out here. I am very thankful.
@craigconstantine also thank you so much for your help!
I had a similar hum when I used my Boya M2 lav mic (worlds cheapest lav mic, but it comes with 6m of cable) into my 2i2 USB interface. It didn’t have a 50Hz frequency, so I assumed it was some other type of EMI, RFI etc.
In the end I got a more insulated 3.5 mm TRS to XLR adaptor and this has fixed the hum.
I’m taking my kit on the road this weekend and trialing the adaptor. Crossing fingers!
