Distortion on the audio even from lower input

Hey I’m pretty new to recording equipment and I was hoping to make a good quality recording within my budget. So far, I spent about $40 to get a USB microphone, the Samson Go Mic (after a friend recommended it and after reading many reviews on it). My problem is that when I’m recording the piano (yes the piano is pretty much out of tune but that’s aside the point :stuck_out_tongue: ) and the problem I’m getting is that I’m having distortions in my audio and this is even putting the microphone farther away from the source (piano) and using the -10dB setting. I tried Cardioid and Omni but those produce WAY more distortion that usual.

I have attached a sample sound file so that others could identify the problem. I’m aiming to get a clean sound while picking up all the dynamics and voices in the piano. My guess is that the culprit lies in the microphone not being able to withstand the loudness of the piano (playing too loud) but I shouldn’t have diminish the overall quality of my recordings just to avoid distortion (thinks of Schubert’s Waltz in A minor.).

I hope to resolve technical problems before I go to a recital hall to record on a grand piano. The piano I’m recording on is an upright piano I have at home and I did it just to test the audio quality of my new USB mic.

The levels look OK. But, I cant’ listen right now, 'cause I’m at work.

Check [u]Windows “Enhancements”[/u] to make sure that Windows isn’t screwing-up the sound.

Normally… When everything is working properly… Audacity captures the “pure” digital data coming in over the USB bus, so normally the only thing that matters is the sound hitting the microphone and the quality of the microphone and it’s built-in circuits. (Audacity itself can’t change the sound during recording but Windows can.)

Usually if you overload a USB mic you get clipping at 0dBFS* (distorted flat-top waves). So it doesn’t look like you’ve overloaded the mic. If the distortion happens only when you play loud then it’s obviously overloading. If you can move the mic farther from the piano, that should help, obviously. If it’s happening when you play quietly, it could just be the quality of the microphone.

So far, I spent about $40 to get a USB microphone, the Samson Go Mic

I don’t know anything about that mic. I assume it’s WAY BETTER than a standard “computer mic” or the mic built into a laptop. And, I always recommend against using the mic input on a consumer soundcard or a laptop. (The USB mic bypasses your soundcard.)

But typically, “studio style” USB mics run around $100 - $200 USD, so $40 is on the low side… But I’m not saying that’s the problem.

With any recording, the performance, instrument, room acoustics, and microphone placement are important. But none of those things should cause distortion. Piano is notoriously difficult to record, but I’m not an expert so I won’t give any advice. You can search the web for suggestions. Just try to ignore the $1000 (or more) microphone recommendations. :wink:

I hope to resolve technical problems before I go to a recital hall to record on a grand piano. The piano I’m recording on is an upright piano I have at home and I did it just to test the audio quality of my new USB mic.

Assuming you can solve the distortion problem, the trick is to get a good balance between direct sound and “room sound” (reverberation). If you are going to rehearse in the hall, try 2 or 3 different mic locations to find what’s best (or experiment by recording someone else’s rehearsal). The “perfect” audience listening position will usually have too much reverb when recorded and played-back on a speaker in a small room. You also need to minimize audience noise (except when they are supposed to applaud at the end :wink: ).

And, I’m always paranoid about using a computer for recording anything where’s there’s no possibility of “take 2”. Computers are the least reliable things we own, plus there is lots of opportunity for human error with computers.

I tried Cardioid and Omni but those produce WAY more distortion that usual.

Cardioid (directional) should be used for almost everything.



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  • 0dBFS is “1.0” (100%) with the default Audacity display and it represents the “digital maximum” of your analog-to-digital & digital-to-analog converters, as well as WAV files, etc.

P.S.

Your mic is rated for 121dB SPL (with the -10dB pad, I assume). Pianos are very dynamic so the peaks will be much higher than the perceived loudness, but I don’t think they peak above 121dB!

I don’t hear any distortion, although the tuning is making my ears bleed. How are you listening? The levels look good.
Can you describe the distortion? I’m expecting crispy ticking and crunching sound if overload is the problem. None of that. Playing in a large, empty rain barrel?

I don’t hear any of that Windows Enhanced Services honking, either.

Koz

You wouldn’t be the first person to discover a speaker problem after recording a clean, clear live performance.

Windows has Playback Enhancements, too. Look for “Concert Hall” or other effects.

Koz

If I had to reveal something, I would pick some of the higher volume notes that get too close to overload. There is one note on the right side (bottom track) near the end that actually does overload. So it’s still too loud.

View > Show Clipping.

We picked -6 as a target for musical peaks in live recordings. Do Not try to make a live performance sound like a store-bought show. Those have been extensively, professionally processed to sound terrific and loud. Once you make a mistake in the live recording, it’s all over. We don’t have good tools to recover from overload or many other recording problems.

http://kozco.com/tech/audacity/Audacity1_record.jpg

Koz

Thanks for the replies and in reply to Koz’s question, the distortion is happening at 00:02 to 00:03 and at 00:06 whenever a loud chord is being played. I will still experiment with microphone placement and using Cardioid to record (since -10dB is not picking up all the details) and let you know of the results. I am also thinking of maybe using a filter on the microphone if the piano is too loud for it. The thing I would rather avoid if possible, is to have to play very quietly in order to stop the distortion or crackle in the sound since that would diminish the overall music dynamics :frowning:

Attached is a picture of the blue waves around 2 seconds. Yes, they’re not supposed to be flat on top (or bottom). This is an overload condition, but chances are it’s not caused by the digital side or the digital converter because there are no overload red bars in Audacity.

You can record at a lower, safe volume and then apply compressors and other effects in Audacity to make up the difference later. Or listen on headphones. As long as you stay within the restrictions of the sound channel you should be able to hear everything in the performance — at the original volume. Once you overload the signal, that’s the end of the story. It’s crunchy city and you can’t stop it.

Your mic is rated for 121dB SPL (with the -10dB pad, I assume). Pianos are very dynamic so the peaks will be much higher than the perceived loudness, but I don’t think they peak above 121dB!

Where did you put the mic? You can get some very serious sound volumes inside a piano, and it’s a good bet the microphone will only stand up to that kind of volume with the -10 button pushed.

Koz
Screen shot 2014-04-10 at 12.44.42 PM.png

I think I fixed the problem, what I did was I turned the microphone input level to very very low like 8/100 or so and then I placed the microphone about 2ft away from the piano. I have recorded at a lower volume (playing the fortes a bit softer than usual) and I think the results are pretty good at least to me :stuck_out_tongue:
I believe my microphone can get to about 15/100 without overloading the signal and I also took into consideration the distance between the microphone placement and the piano.

I have attached two samples one with the lower input volume non-compressed and one that has been compressed after recording.
I also played a little bit softer than usual so here are the results. I’m pretty satisfied with the results.

And you can inspect the blue waves just like I did if you think there is any damage. Drag-select one of the very high peaks (either direction) and Magnify Selected (Control-E). Keep doing that until you get close enough to the wave peaks to check for damage. It’s Most Unlikely for music waves to have flat or inverted tops and bottoms. That sounds terrible.

Zoom Full (Control-F) to return to the whole show waves.

http://manual.audacityteam.org/o/man/zooming.html

Koz