It’s a spoken message and there are lots of crackles on the peaks. I’m guessing it’s some sort of digital clipping. It was recorded from a yamaha 0V1 digital desk onto minidisk and from there recorded back into an audacity project. The crackle is on the minidisk but wasn’t noticable on the house speakers so perhaps it was on the auxilary channel that was used for recording. I’ve tried lots of effects but nothing much makes a difference.
Any ideas appreaciated.
Link to sample file http://www.mediafire.com/file/wyigoitbann/akSamp2.mp3.
You can help a little by brute force filtering them out. Everything after “Good Morning.”
That’s a low pass filter 24dB, 5100Hz in Audacity 1.3.7. This works because most of the cracking is very high frequency, but I can’t do much better than that. It’s not clipping. There was a data error somewhere.
Digital transfer? Has this always worked and suddenly this day, it did not?
No it’s not digital transfer or recording but analogue.
The original file is much bigger 40 minutes or so and the problem is there on the whole file. Usually we don’t have a problem with the recording as long as the levels are reasonable - which they were in this case.
I will give the low-pass filter a try. Thanks for your advice.
I’m going to try recording directly onto the laptop with Audacity next time.
Not clipping, it sounds more like self-modulation to me.
I’ve had a go at “healing” it (attached) , but I’ve just swapped one type of distortion for another.
akSamp2_before-after (mono) (mp3 in zip).zip (431 KB)
<<<I’m going to try recording directly onto the laptop with Audacity next time.>>>
You can easily record directly to a Mac laptop. Most PC laptops do not have a Line-In but a Microphone input. The robust, powerful, Stereo line signal from the mixing desk will overload a connection expecting a tiny, delicate mono microphone signal.
What effects did you apply to “heal” it?
So what is self-modulation in audio terms?
I’ve had another go based on the suggestion of kozikowski. Here’s how:
- Used Noise Removal to get rid of the background noise.
- Applied Low Pass Filter a bit more agressively than suggested (36db 0.7q 3621 Hz)
Here is the result: http://www.mediafire.com/file/jdzgijmyddk/ak_fixed_before_and_after.mp3
I think that’s about as good as you’re going to do. You basically turned it into AM radio, but that’s OK if the presentation is pleasant and the subject is engaging. The presenter has a nice voice.
The bulk of the noise during the voice seems to be caused by the voice. When the voice stops, the bulk of the trash stops, too, leaving just the background hiss. We get that in the studio when the digital connection between the rooms becomes damaged.
Hiss may be a clue, by the way. Is there significant hiss in the live presentation or present in headphones on the mixing desk? That can happen very badly if you have data errors.
Could this be something silly like the mini-disk is running low on batteries?
Connect an iPod or other high-quality music player directly to the mini-disk and see if you get a good transfer. I’m a grand believer in splitting the system up to see where the problem lies.
Yeah I realise I lost some of the quality of the voice but I think that is less distracting than the crackles and hiss.
It’s a mains based minidisk deck (Sony MDS-JE33C) rather than a portable one. Good idea about pluging something else directly into it though. I’ll give that a go.
There isn’t significant hiss on the headphones or live presentation that I remember but I’ll pay more attention to it next time. It could be all sorts of things - I will try and eliminate them methodically. I usually give more of my attention to the live sound than the recording which probably doesn’t help! The microphone is a wireless handheld Sennheiser model which is usually perfectly good for the purpose.
Thank you very much for all your ideas and help.