Here is my third version of oscilloscope with memory 

I did try to stay UX as close as possible

Input select:

Doesn't do much on my computer but for some sound cards will have the difference. You need to know what microphone input is from available in drop down.

Screen width:

Time during bytes shown on screen were collected;

Browser has special class: ScriptProcessorNode connected to audio steram. Node reads bytes in array (buffer size). In this case buffer is 2048 bytes

ScriptProcessorNode triggering javascript function every time buffer size is processed.

This function read  bytes from buffer and draw it on screen;

Time difference between triggers shown as Screen width.

Record total Screens:

Number of packets (buffers) will be hold in browser memory ready for processing

Sensitivity:

Only array will be recorded if array contains value exceeded sensitivity value

Accepted values from 0 to 128

If value is 0; all packet will be recorded;

Print Recorded:

Functionality in development

For now it gives you all recorded values in text area;

each row starts from timestamp and ends with \n symbol. Data between represents buffer data as coma separated array;

Bottom screen is for viewing recorded buffers; Range slider navigate between buffers (draw each packet on screen);

Number on the right is total buffers recorded;

Try to brake it. If you do please let me know.

I'm working on next version 4. I feel like missing capability to see all recorded packets at once

This how it looks om my computer:

If you want to save oscillogramme  on PC right click on graphics -> save image