low motorboat sound running under audo

[lclayton]

Sorry all, I am a newbie at this audio recording, but I am trying to create an MP3 file which will then be integrated with a PPP in Slideshare.
Anyhow, I using a Logtech mike and have recorded some tests audios, but when I play them, they all have a kind motorboat sound...da,da,da,da,da,da, etc....running underneath. I am using Windows 7. I am sure the settings are wrong, the device is wrong, something is wrong, but when I look at the menu and the drop downs and the help index, I can't even begin to understand it. Thanks for any suggestions.
Larry

[Trebor]

Thanks for any suggestions.

1. remove or disguise the email address in your post, otherwise you could be sent spam emails ... http://en.wikipedia.org/wiki/Email_harvesting

2. attach 5-10 seconds of the motorboat sound to your next post, or provide a link to were we can download / hear it .

[lclayton]

Trebor. Thanks will do. Have removed email address. And will attach a 5 or 10 second copy of an audio with the sound. Just need to figure out how to do it.
Larry

[lclayton]

Trebor,
Here are two recordings, one in MP3 and the other one in Audacity's proprietary I guess format.
Larry

[Trebor]

Your motorboat is a 15Hz signal and its harmonics, (multiples thereof, i.e. 30Hz, 45Hz , 60Hz, 75Hz … 9375Hz).

lclayton's motorboat.png (22.52 KiB) Viewed 2112 times

IMO this sound is an artifact generated by the recording device, ( I have an $ 25 pocket voice recorder which does something similar, example attached )

Because the harmonics go across most of the audio spectrum and are very close, (only 15Hz apart), it’s impossible to remove them without totally mangling the audio.

You'll need another recording device to avoid the motorboat. If you used the computer's internal sound card to record an external sound card or a USB microphone may give better results.

[lclayton]

Trebor,
Thanks. So, you are suggesting a higher quality microphone? Or some other alternative? I just bought this logitech yesterday and I thought it was the best of two or three that Best Buy had on sale. I'll certainly spring for something higher if I need to since this is a medium I wish to pursue with some of my web sites, blogs, advertising books, etc.
Larry

[Trebor]

So, you are suggesting a higher quality microphone? Or some other alternative?

The motorboat sound is an artifact of the audio capture device: if you plugged the mic into the computer then that's the computer's internal sound card that's the problem. Plugging a different microphone into the same sound card won't change the motoboat problem one bit.

USB microphones plug into the USB port of your computer and don’t use the computer's sound card, so could give better results than your current set up..

An external sound card is another option (shouldn't have or pick up clock noise harmonics).

[lclayton]

Trebor,
I know these seem like simple questions (probably because they are!), but I still am getting the motorboat, even when plugging in the Logitech mike via USB port. However, I am don't know if in the devices screen of Audacity Preferences I am making the right selections in the different boxes.
Under Interface:
Right now I have MME selected under Host. It does give me another choice, Windows Sound Select
Under Host it has Using and says "PortAudio V19-devel (built March 29 2010)
Under Device, I have elected Speakers (Sound Blaster X-Fi Xt, although it gives me two other options: Microsoft Sound Mapper (output) and Digital Audio (S-PDIF) (Sound B

And under Recording, Device I have selected Microsoft Sound Mapper-Input, but have the following options: Microphone Array (Monitor webcam) and Digital Audio (S-PDIF) (Sound B

In other words, while the Logitech green led light is one and it is plugged in, I don't know if I am recording through it or the computer's sound card.
Larry

[Trebor]

Sorry, my mistake, I thought you had a mic plugged into the 3.5mm mic jack socket on your computer, I didn’t realise you were using a mic which plugged in the USB.

Two things worth trying with your USB microphone ..

1. disable all the other recording devices in the windows recording devices, just in case one of these other devices is responsible for the motorboat sound .

2. increase the level slider in windows recording devices for the USB device : it may increase the voice level without increasing the motorboat, i.e. improve the signal to noise ratio.

Your test2.mp3 only has frequencies up to 16KHz, this corresponds with a sample rate of 32KHz ...

frequency analysis of 'test2' ends at 16KHz.png (8.84 KiB) Viewed 2079 times

The default sample rate on Audacity is 44.1KHz, but it can be set to 32KHz: Audacity 1.3, "Preferences", "Quality", "Default sample rate", (I’m not optimistic doing this will make any difference).


http://logitech-en-emea.custhelp.com/ap ... /gb,en/kw/

[lclayton]

Trebor,
Thanks. I'll try that. I'm off to Church. Maybe I can pray it into working right!
Larry