waveform position indicators

[JasonDS]

I would like Audacity to show the waveform position at the start and end of the selected area. (not how loud the sound is but where the wave form is currently in the vertical position, +0.23, -0.47 ext.) This would make it easier to know where to cut and not get a "pop" sound. Also it would help to show where you could loop the audio and not have a "pop" when Audacity or an audio player jumps back to the start of the audio clip.

[steve]

Audacity is able to snap to zero crossings (if there is a zero crossing near to the ends of the selection). See: http://manual.audacityteam.org/man/edit ... .html#zero

[plunderingsloth]

Clicking "Find Zero Crossings" fails to align the cursor along the intersections of the waves and the 0-axis, as demonstrated in the attached picture.

Find Zero Crossings.jpg (333.57 KiB) Viewed 1028 times

Therefore, using the tool fails to eliminate the popping noise that results from clashing waves.

Am I doing something wrong? Does it simply not work in areas of such quiet audio?

[steve]

Am I doing something wrong? Does it simply not work in areas of such quiet audio?

I think that the problem is not the amplitude, but the frequency. The frequency of that big slow wave looks to be about 14 Hz - the distance between consecutive peaks is about 0.07 seconds (wavelength = 1/frequency). The distance that the end of the selection would need to move to find a zero crossing point is about 1/4 cycle (about 0.0175 seconds, which is about 770 samples). That's too far for the zero crossing detection.

The "noise" shown in your example is mostly sub-sonic rumble. The solution is to fix that first by using a high-pass filter.
What is it a recording of? The type of audio is important when deciding the best kind of filter to use.

[plunderingsloth]

Hey Steve,

This is a voiceover recording, and the selection in the picture is my room tone.

Generally, I cut out bad takes first and THEN perform a high pass filter set at an 80Hz frequency, but the bits where I made the cuts leave a popping sound.

I found out that "Find Zero Crossings" is supposed to help eliminate the popping sound, but--as mentioned--it doesn't actually quite line up at the axis.

Is there something I can do here to eliminate the need to manually line the cursor up at 0 crossings?

[kozikowski]

I cut out bad takes first and THEN perform a high pass filter set at an 80Hz frequency

I would so strip out the rumble first. Many microphones create their own rumble and it doesn't stop at 20Hz, the lower limit of hearing. Many microphones are still generating digital garbage down at 2Hz and 3Hz. That data gets into effects and filtering tools and makes them act funny.

Koz

[steve]

This is a voiceover recording,

Then it's safe to take out frequencies below 80 Hz (for music you would usually want to retain frequencies down to at least 50 Hz).
Has koz pointed you to the "low roll-off for speech" preset for the Equalization effect?

Generally, I cut out bad takes first and THEN perform a high pass filter set at an 80Hz frequency

As koz wrote, better the other way round - deal with DC offset and rumble first. A rumble filter will take out DC offset, so if you use a rumble filter that takes care of both issues.