Something Strange With Recording

[Gary999]

I hope this is the correct section of forum, but in the image you can see where something strange happened in the timeline of a recording. Theres is a difference in the sound, but only slight. As you can see there is a big difference in the apperance of the timeline. The microphone was recently checked and passed by the manufacturers, so I am thinking I may have a problem developing with mic lead or interface, because occasional odd strange noises in recordings have arisen recently, hence the reason for having the mic checked.

It is a voiceover recording with no other sound and recorded in a sound booth. I initially thought I may have left the desk mic open which is a possibility. But there was no sound in the persons headphones to be picked up by the recording mic and the desk mic requires no phantum power. But both mics are going through the interface an Audient id14 mk1. Even so, if I had left the mic open and introduced some noise, it still wouldnt have affected the recording timeline, or would it?

Has anybody any ideas?

Thanks.

 

[rob aylestone]

Purely based on the display, you're concerned by the bit in the centre where the display shows a change when there's nobody speaking? First thing, forget the cable - they can crackle, and they can even be microphonic - producing noise when you thump them, but what you are showing here is frequency content display - with low frequencies at the bottom and high at the top and time running left to right. All that seems a bit weird is the energy right at the bottom, and it's quite narrow band. It's electronic in generation. It could easily be a condenser mic that is unstable, but I doubt this would be picked up by a service department unless you also sent them that image? I've never know one produce a rumble like that. My best guess is the preamp. The fact that there was almost silence, then a sudden start to it again in the middle sounds like something in the preamp changed. What does it sound like? Probably a clip of the section that the image comes from would be best. The cut-off of the noise at the bottom is quite sharp? Do you have anything else, interface wise, you can try?

 

[Gary999]

Hi Rob thanks for the reply.
The verticle line is where I have saved the previous recording and the continued recording has started again. I save after or delete and retake after every sentance and the saving/restart produces that line. You can see it is two different files in reality on one long timeline.
The mic is a 103 and was recently sent back to Neumann who checked and passed it. But my reason for doing this was sporadic strange noises or distortion on recordings. So check mic out first. Sometimes I get a hum appear at about 120dbs but easily got rid of. I have seperated cables etc and even taped them to walls to seperate them.
But this visual thing is something new. I could have left the desk mic open, but I wasnt talking in to it and there was no other sound.
What concerns me is that it obviously affected the recording although hardly audiable but certainly visual. The jaggedness of the recording is there at all dbs and not down at 120dbs.
Confused. I thought it could be my mic lead or the Audient. I cant think of anything else.

 

[rob aylestone]

If something hums, then it could be a cable fault, but the 103 needs an electrically OK cable or the phantom doesn't work. The 103 is actually a bit of an odd circuit design - it's transformer-less and is sort of really an unbalanced circuit in the mic, that relies on the preamp, providing the differential return. I don;t really get the visual problem - the waveform looks pretty typical - I worry about things I can hear, NOT what I can see. The waveform generation often produces waveforms that don't at first glance match what you hear. Cubase occasionally does this, and has less resolution in the waveform - I've never found a way to change the display, but I think you are saying that the change in that bottom line is just an edit from where you had a hum to where you didn't.

If you post a .wav file we can load it onto our software and have a proper listen - we cannot diagnose what we can't hear?

 

[Gary999]

Here you go Rob. Cut from the timeline and it is 2 takes. The one before and the one after when it goes all squiggly, but both from the timeline. Raw unedited, but in mp3 as .wav will not load on here. Recorded in Reaper. Exactly but a bit more than what you could see in the image I posted at the start. Regards the occasional hum, I dont think that is present here in any great volume.
The hum can be sporadic and there is nothing in the studio switching on or off to cause electrical interferrence except the processor fan on the pc. This cannot be heard by the mic, but I suppose it could be an electrical item switching on and off as it boosts to cool down the processor. It does not cause that squiggly stuff in the image. These takes are at the end of the total recording, the final few minutes of an hours take and the processor cooling fan had been on many times in that period without squiggly recordings showing up on the timeline. The squiggly part went to the end of the recording.