Science Buddies: "Ask an Expert"

So i downloaded the program Sound Forge 8.0, which was exactally what i was looking for, but then it dawned on me, i have no idea how to use it.

so i was messing around on it, and i found this thing that gives you the statistics of a selection of a portion of the soundwave projection, and i found this thing that tells your the "zero crossings" in Hz. i looked on the help and it says "The number of times per second that the waveform changes from a negative value to a positive value."

can anyone explain to me what this means?? and is this of any value to me trying to find changes in the sound waves between two different CDs?\
is this a good thing to compare?

thanks =)

You should be able to compare the sound waves from each cd using that software.
The shift from positive to negative can be demonstrated by watching a speaker vibrate in and out.

Hope this helps-I may be able to give you more information if you give a little more detail about your experiment.

danielbickford wrote:You should be able to compare the sound waves from each cd using that software.
The shift from positive to negative can be demonstrated by watching a speaker vibrate in and out.

Hope this helps-I may be able to give you more information if you give a little more detail about your experiment.

The details of this experiment are located in another thread. Basically, the student wants some metric to determine how damaged a cd is by heat or light.

I think you want to compare the enitre waveforms and not just the zero crossings. If you can get the waveform out it numerical form, then you could easily compare the two. For example, you could say- if there is no damage, the waveforms should be identical, so if I subtract them, I will get a table full of 0s. If they are different, then I will get non-zeros. There are specific formulars to measure this type of thing- if you can get this data, then we can talk about formulas.

I don't know how Sound Forge works, but in a sound editing program I have you can get a frequency spectrum--if you could get that in some kind of numerical format (rather than the visual format my sound editing program gives) you could compare the frequencies two bits of music. Amplitude would be another important metric.

The details of this experiment are located in another thread. Basically, the student wants some metric to determine how damaged a cd is by heat or light.

I think you want to compare the enitre waveforms and not just the zero crossings. If you can get the waveform out it numerical form, then you could easily compare the two. For example, you could say- if there is no damage, the waveforms should be identical, so if I subtract them, I will get a table full of 0s. If they are different, then I will get non-zeros. There are specific formulars to measure this type of thing- if you can get this data, then we can talk about formulas.

^^^
this is exactally what i want to do.

THANK YOUU. =)

i just have no idea how to get it into numerical value.
anyone know how i could do this?

Hi,
I don't know Sound Forge, but I do know Audacity:
http://audacity.sourceforge.net/
With audacity, you can run a frequency analysis and export that file as text. Use "Analyze" -> "Plot spectrum" -> "export". I'm not sure if that meets your exact wishes, but it is a possibility.

Go here: http://www.sonymediasoftware.com/downlo ... sp?DID=559 and download the manual for Sound Forge. Then read Chapter 18 starting on page 275, all about frequency analysis. Looks like you go to the View menu and then hit 'spectrum analysis.'

Turns out you can actually take 'snapshots' of the spectrum analysis and the program will compare them for you. (page 282 in manual) I couldn't find anything that would allow you to export it as text, but it might be somewhere else in the manual and it sounds like you can compare the two spectrums directly using the program so that step may not be necessary.

Man, this is better than the sound program I use!

MelissaB wrote:Go here: http://www.sonymediasoftware.com/downlo ... sp?DID=559 and download the manual for Sound Forge. Then read Chapter 18 starting on page 275, all about frequency analysis. Looks like you go to the View menu and then hit 'spectrum analysis.'

Turns out you can actually take 'snapshots' of the spectrum analysis and the program will compare them for you. (page 282 in manual) I couldn't find anything that would allow you to export it as text, but it might be somewhere else in the manual and it sounds like you can compare the two spectrums directly using the program so that step may not be necessary.

Man, this is better than the sound program I use!

Yeah, it seemed nice. More importantly, it has a free trial, so for a one time project like this, it is perfect!

Louise

thanks for the audacity tip.

i downloaded it and i want to try it, but it isnt compatible with CD format.

does anyone know of a program that converts files to a different format or how i can do this??

Here is one program:
http://www.exactaudiocopy.de/
and here are some additional possibilities:
http://en.wikipedia.org/wiki/CD_ripper#Windows
iTunes will do the conversion, though I'm not sure what file formats it will permit as output. Windows Media Player will only allow output to Windows Media Audio files, which is not very helpful.

Audacity can convert to MP3 or Wav files. I use it at home to make mp3 ringtones for my cellphone, and I know that it can do those conversions.

Look in the File Menu. It has choices for "Export as MP3" and "Export as WAV". Both are CD compatible, if I am understanding what you mean.

Otherwise, there are many programs that will do the conversions. Musicmatch, Windows Media Player, etc.. All are free in some versions.

okay, i downloaded audacity, and it was sooo perfect. thank you for the tip.

so i got a text reading and it says frequency (H) in one column with a bunch of numbers, and then level (dB) in the next column with a bunch of numbers. can any one help me make sence of this text??? i can kinda understand teh frequency, but what is the level?

thank you. =)

dB stands for decibels, which is a unit of measurement for how loud sound is. So what that information is telling you is how loud the sound is at each frequency.

Hope that helps!

thank youu. =)