Audacity Forum

stevethefiddle wrote:Something I've noticed on several recordings so far is that there's been a bit over-emphasised at about 100Hz, which could be giving the impression that some of the recordings are more bassy than they really are. I can't tell why it's happening - mic position, microphone, the room, or whatever, - but the next time you get a recording that sounds a bit bass heavy, try using the equalizer effect in Audacity and just dropping the 100Hz a bit.

Where do you see that 100Hz emphasis? Looking at the frequency spectrum plot I can't see any peak at 100Hz...

<<<I can't see any peak at 100Hz...>>>

You may not. I think he's hearing it. On the spectrum, it would not necessarily look like a "haystack" at 100 Hz. It may be nothing more than a relatively out of balance blob of energy at about 100Hz compared with the rest of the spectrum. It wouldn't stick out unless you compared the musical notes directly with a spectrum of better balance.

This is where you get into the quiet room and expensive guy (in flip-flops and ponytail) in Hollywood doing the final mix on your show.

He not using meters.

Oddly, I don't know any girls doing this.

Koz

You may be messing about with a microphone in a hallway. We're preparing your clips for commercial release.

Koz

kozikowski wrote:This is where you get into the quiet room and expensive guy (in flip-flops and ponytail) in Hollywood doing the final mix on your show.

He not using meters.

That's what I was afraid of... I have a pair of flip-flops and I could let grow a ponytail... but I don't think I could educate my ears in such way... But that's probably why I'm still recording in the hallway and not playing at the carnegie hall...

kozikowski wrote:Oddly, I don't know any girls doing this.

Maybe girls in ponytails and flip-flops have better things to do... Anyway looks like there might be some out there:
http://www.shamelessmag.com/issues/2004 ... -engineer/
(and she has a portuguese surname )

I've got the ponytail (no flip-flops - too wet and cold here)
Let's have a look at a couple of spectra (spectrums in the vernacular).
(BTW, if you click on these images it should expand the pictures to remove the scroll bars)

First lets look at "34-art-usb-sample2-stairway".
This one sounds gorgeous, no over-emphasis here, just a nicely balanced sound - this can be our bench-mark.
Now that's interesting - see the spike on the extreme left (if I cursor over it I'm told 82Hz). That's the bit that gets hacked by the low frequency roll-off.
Then there's a bunch of three spikes (98 110 124 Hz according to Audacity). I'm betting that we will see one or more of these at a much higher level in some other recordings.

Here's "31-art-usb-dual-pre-sample1". Not to say this is a "bad" recording - it's still very nice, but every now and then I hear a "whoomph" - where's that coming from? Let's look at the spectrum.
See the spike at 110Hz (got the cursor in the right place on this one ) Much more pronounced than in the first picture.
If you listen to the recording (listening is after-all the important part), then at first listening it probably sounds fine - nice and warm with plenty of detail.
But listen again - that note at 15.5 seconds - "whoomp" - what is that? Bottom "A"?

I tune to "A 440", so that would put a bottom A on the guitar at 110Hz.
The good news - your guitar is in tune.
The bad news - whenever you hit an open A string the fundamental of the note will be over-emphasised (with the exact set-up that you used in this particular recording).

What did you do different between recordings "34-art-usb-sample2-stairway" and "31-art-usb-dual-pre-sample1"?
I'm not sure - you probably put it in the notes a few pages back in this thread, but I've got the bath running so I can't look now. Probably just catching a bit more from the sound hole in the second one.

Guitars are supposed to resonate at around 100Hz (and at around 80Hz) - it gives depth and warmth to the tone, but when recording it is very easy to pick up too much from one part of the guitar and get a recording that is out of balance. (The 80Hz resonance is typically the one that feeds back first with live PA and is just above the bass roll-off frequency on a lot of mixing desks - fortunately it's pretty easy to tame).

I was looking at the spectrum plots with the settings at "size: 512" I changed to 16384 and all of a sudden there was so much more details, specially in the low freqs... I can see the light now hehe thanks!

Newbie little mistakes here I guess... Reminds me of the first time I had to program a PIC microchip... one of the i/o ports had a default configuration different from the rest of the ports... which I wasn't aware of... and that drove me crazy for a couple of hours... until I found that little footnote somewhere deeply burried in the manual...

About the sample 31... one thing that's different from the other recording is that the top string is tuned to D rather than E...
At the 15.5s it's the end of a "sentence" right before the beginning of a new one. The ending "sentence" ends with an A on the bass, which acts like a "full stop". Right before I start the next "sentence" I have to muffle the A string with my thumb so that it won't overlap with the next chord. Maybe that helps explaining that "whoomp".

Sometimes this is also the kind of moment in the recording that you might hear my breathing... One technique that helps getting the right tempo and pace into the song is to sync it with the breathing, like a singer does... Because the mic is standing rather close to my face it's not uncommon to catch me taking a deeper breathe at this points... I've been more actively trying to control my breathing while playing for the last few days because of this...

Edit: just to add that the sample 34 has only two A's on the bass (somewhere in the middle) and the sample 31 has a lot more A notes on the bass...

<<<Sometimes this is also the kind of moment in the recording that you might hear my breathing...>>>

There was a posting on the forum from someone looking for a way to filter all those out.

Bad. Idea.

Koz

kozikowski wrote:<<<Sometimes this is also the kind of moment in the recording that you might hear my breathing...>>>

There was a posting on the forum from someone looking for a way to filter all those out.

Bad. Idea.

Koz

I don't want to filter it, just trying to avoid the source of it (well... avoid enough without fainting and turning purple )

Try not to hit the microphone if you fall forward.

Koz

bgravato wrote:I don't want to filter it, just trying to avoid the source of it

How about placing the microphone a little lower?
Sometimes it's easier to position the microphone lower if you turn it upside down so that it's "hanging" rather than standing up.

bgravato wrote:I have to muffle the A string with my thumb so that it won't overlap with the next chord. Maybe that helps explaining that "whoomp".

That certainly accounts for some of the tonal difference on that note, but the resonant frequencies can be seen throughout the recording. That's completely normal - it's some of the guitars natural resonance. The issue to notice is that if the microphone is picking up some of these natural resonances more than others, then notes that are harmonically related will be exaggerated. This effect being most pronounced when the fundamental frequency of the note coincides with a resonant peak.

There are various reasons that certain frequencies may be more prominent than others. Microphone position plays a very large part, and for the low frequency resonances the position of the microphone in relation to the sound hole plays a major part. Also the room will have an effect. When I'm setting up a PA system in a new venue, one of the first things I'll do is to walk around the room and make a sharp "clap" with my hands - listening to how the sound of the clap rings provides a lot of information about the acoustic properties of the room. One of my regular venues has a strong resonance that coincides with the note "D" - a nightmare for acoustic folk bands.