How to suppress severe background hiss on magnetic tape?

[Oliver33]

Hi. First post. All help appreciated.

Twenty years ago I conducted about sixty hours’ worth of interviews that I recorded on tape. Back then I was only interested in the info I was getting, so the sound quality is pretty bad. Fast-forward twenty years, and I’d like to preserve the interviews by digitalizing them. But I’ve hit a few snags.

My main problem is the background noise – not the intermittent noises that are easily distinguishable from voices (ticking clocks, birdsong etc.) – I don't care about those – but a persistent hiss across the entire frequency range. On some tapes it practically drowns out the conversation. (When I play the actual tapes on an old cassetter player, the voices are far better distinguishable than when I play the files on my computer.)

I’ve been using Izotope RX 4 to deal with the issue, and I’m fine with what I’ve been able to achieve on most of the recordings, but there are about ten hours’ worth where "equalizing," "gaining" and "dehumming" aren’t good enough, "leveling," "denoising" and "deconstructing" distort the vocals too much and "declicking" has no noticeable effect at all. Is there some other program that can deal with the issue better than RX can?

Also, could appreciably better audio be achieved with a better digitalization setup? My cassette player is a Sanyo BassXpander, it’s connected to my computer via a DeLock Sound Adapter 7.1, the program I use for playing the tapes into my computer is Audacity 2.1.0, and my computer is an iMac (OS X 10.9.4, 21.5 inches).

What could I upgrade that would make a real difference? Am I correct in assuming that a quality „audio interface“ instead of a twenty-dollar DeLock Sound Adapter would be helpful? If so, what should I be looking for in an audio interface for my particular purposes (speech with background hiss on magnetic tape, mono). And what price range are we talking about (I'm willing to pay more to get more)?

Two related questions:

– I’d like to digitalize the audio with Izotope RX instead of Audacity, but RX doesn’t list the DeLock Sound Adapter under Preferences/Audio/Input device (although it does list it under „Output device“). I couldn’t find a fix via Google. Any ideas?

– Most of the sound files I’ve derived from the tapes have sections of varying length that exhibit numerous brief gaps or jumps in the audio (for some reason this doesn't apply to the first seven tapes, which don’t have this problem). The gaps are definitely computer-generated: they’re not present on the actual tapes when played on the cassette recorder. The gaps occur even when I take care to close all the other programs on my Mac before I record. Audacity’s preferences are on their defaults values. Suggestions?

Again, any input would be greatly appreciated.

 

[bouldersoundguy]

As for the gaps look into optimizing a Mac for recording. I use a PC so I don't know things specific to Macs, but it usually involves turning off antivirus software and the wifi.

There's only so much you can do to mitigate severe tape noise, especially with affordable software. One thing that can help is to maximize your signal to noise ratio before the signal even gets to the computer. What I do is adjust the azimuth to the recording. That brings out all the available treble content from the recording without affecting the noise, giving you a slight advantage when trying to denoise the digitized audio. Also, a recording made on a mono tape deck may be less noisy played back on a mono machine than on a stereo machine.

 

[Oliver33]

Points taken, thanks.

One thing I'm curious about is, do you think I could benefit by getting a higher-quality audio interface than the ultra-cheap one I have now?

 

[bouldersoundguy]

Points taken, thanks.

One thing I'm curious about is, do you think I could benefit by getting a higher-quality audio interface than the ultra-cheap one I have now?

If the tape noise is really substantial then whatever the interface adds that's of similar character won't make much difference. Recording in 24 bit probably won't help much as the tape noise floor is so high the dynamic range of 16 bit is more than adequate. As long as you're getting a reasonably clean capture it should be fine. What do you have, one of those Behringer UCA devices?

 

[miroslav]

If you are going to spend money....just buy a de-noise/de-hiss/de-click application that you can use to clean up the problems.
That might be your best option for already existing, digitized audio.
Google is your friend...there are a few apps out there (some expensive).

Here's a fairly cheap one...the more expensive ones have deeper features and quality...but this might work for you.
MAGIX Audio Cleaning Lab

 

[Oliver33]

I can't believe it! In view of Bouldersoundguy's advice about using a mono machine, I did just that, but the sound quality was worse than ever (no wonder, I used the twenty-year-old cheap device I used to record the interviews in the first place). So I went back to the stereo machine I'd been using. BUT … meanwhile I'd inadvertently changed the volume control on the stereo machine, and since I didn't know where it had been before, I just left it where it was. Then I opened Audacity to make another recording attempt, and it turned out the volume was too high. But instead of adjusting the slider on the cassette player, I adjusted the relevant slider in Audacity … and the sound is perfect now! – or at least way more than sufficient for my needs and better than I ever could have imagined! Awesome! So thanks, Bouldersoundguy, even if your advice only solved my problem indirectly. This is awesome!

Take care, everybody!

 

[Oliver33]

Thanks again for the response I hadn't seen before, and thanks also to Miroslav.

Have a great weekend, guys.

 

[bouldersoundguy]

By the way, I strongly suggest demagnetizing the heads of any deck you play those old tapes on. A magnetized head will partially erase the recording each time you play it. Demagnetizers are cheap. Get one and read the directions carefully before using it. Keep all magnetic media well away from the area when demagnetizing heads.

Also, get some 99% alcohol and some cotton swabs. Clean the heads and other parts of the tape path. Let the alcohol evaporate thoroughly.

 

[Oliver33]

Will do.

 

[Steenamaroo]

As for the gaps look into optimizing a Mac for recording.

I wouldn't recommend doing that. Performance isn't really the issue here, and optimising isn't a good term to search for in relation to apple software.
Bogus companies prey upon uninformed users and you'll end up with all sorts of useless or unnecessary bloat.
Your mac is pretty much as as optimised as it needs to be from the factory.


If the recording has noise but playing straight from cassette doesn't then either the input device, or line outputs, are noisy.
I take it you're using a line out, not headphone?

If you can find a way to prove one or the other that'd be great but, if not, a good quality tape deck and half decent audio interface (Even unbalanced line-only) would probably make a decent different.

Edit: I see you've had success. Glad to hear it.

 

[bouldersoundguy]

I wouldn't recommend doing that. Performance isn't really the issue here, and optimising isn't a good term to search for in relation to apple software.
Bogus companies prey upon uninformed users and you'll end up with all sorts of useless or unnecessary bloat.
Your mac is pretty much as as optimised as it needs to be from the factory.

I'm not talking about loading up the computer with odd bits of "performance enhancing" software, just disabling the things that can interrupt audio performance. Since the earlier transfers were done without problems it's probably something simple that changed and just needs to be changed back.

 

[Steenamaroo]

I actually missed what he said about gaps in recording so performance was relevant but yeah, I'm just suggesting that the OP shouldn't "look into" optimisation for mac because it's a common bait term online.

 

[bouldersoundguy]

I actually missed what he said about gaps in recording so performance was relevant but yeah, I'm just suggesting that the OP shouldn't "look into" optimisation for mac because it's a common bait term online.

I would use "optimize Mac for audio recording" to target legitimate audio-specific advice. I figure if people haven't learned to recognize bad sites and links by now they're beyond my help.

 

[Steenamaroo]

I would use "optimize Mac for audio recording" to target legitimate audio-specific advice.

With respect, that's my point.

 

[Massive Master]

Usually when I run into tapes with excessive hiss, it's because they were recorded with DNR or something engaged. Possibility? Already covered?

 

[ecc83]

Good that the OP has had some success but I have found that USB device and boy, is it cheap!

I would also suggest the Behringer UCA 202/222 interface as more than good enough for tape dubbing.

For noise reduction I have used Sony Soundforge and the idea is you get all the recordings "in the can" then download the 30 day trial and get busy!
MAGIX have scooped up all the Sony media apps it seems but I have dealt with them for 10 years and although they can be a bit stiff and "German" they are alright.

Be a bit careful with a degausser, you can maker matters worse. With a cassette machine you can usually de-mag the head by putting the machine into record mode (BLANK CASSETTTE!) a few times. Good idea to do this anyway because if not used for months/years the REC/PLAY switch contacts tarnish and you can get instability, twitterings, squeals, on playback.

Dave.

 

[FingerzAndKeyz]

I can't believe it! In view of Bouldersoundguy's advice about using a mono machine, I did just that, but the sound quality was worse than ever (no wonder, I used the twenty-year-old cheap device I used to record the interviews in the first place). So I went back to the stereo machine I'd been using. BUT … meanwhile I'd inadvertently changed the volume control on the stereo machine, and since I didn't know where it had been before, I just left it where it was. Then I opened Audacity to make another recording attempt, and it turned out the volume was too high. But instead of adjusting the slider on the cassette player, I adjusted the relevant slider in Audacity … and the sound is perfect now! – or at least way more than sufficient for my needs and better than I ever could have imagined! Awesome! So thanks, Bouldersoundguy, even if your advice only solved my problem indirectly. This is awesome!

Take care, everybody!

So, did you have the output of the tape machine too high and digital record volume too low? If that's what was going on, that would dramatically increase hiss for sure. Also, make sure you have the tape machine plugged into the correct kind of input (i.e. line input to record, if you are coming out of the line out of the tape machine), so you don't increase hiss that way.