Method for checking if digital data is transmitted accurately?

[MissP.25_5]

In this experiment, a person's voice was recorded on a mic as the analog source. And then the analog data was converted into digital data so that the program on the PC could read it and then the digital data was converted into Analog again to reproduce the recorded voice. I attached the results of the last part of the experiment. I am not sure what method this is. What I do know is that it is done to check whether the digital data was transmitted accurately or not by using the A/D and D/A conversion program on the PC. Can someone explain to me what exactly does that picture mean? What is being done here? The AD and DA waveforms are the same after adjusting the trigger level (Voltage). The writings are just the settings of the sampling. The sampling frequency is 8kHz. I want to know what does the trigger level have to do with checking the accuracy of the digital transmission? What is the disadvantage of this method and how to improve it?

 

[Vengateswaran]

Can you attach your experiment.

 

[MissP.25_5]

Can you attach your experiment.

I forgot to attach it. There I attached it.

 

[BradtheRad]

Probably the most useful result of this experiment is that it tells you objectively where you start losing high frequencies by using a sampling frequency of 8 kHz.

As a further experiment, you would listen for differences, and make a subjective comparison.

This A-to-D and D-to-A process is how we listen to CD's, digital TV, and internet audio.
CD's in particular sound better, because they use a higher sampling frequency.

 

[MissP.25_5]

Probably the most useful result of this experiment is that it tells you objectively where you start losing high frequencies by using a sampling frequency of 8 kHz.

As a further experiment, you would listen for differences, and make a subjective comparison.

This A-to-D and D-to-A process is how we listen to CD's, digital TV, and internet audio.
CD's in particular sound better, because they use a higher sampling frequency.

So you mean, this is a comparison method? What is the disadvantage of this method?

 

[BradtheRad]

So you mean, this is a comparison method? What is the disadvantage of this method?

* The oscilloscope-type displays are a good first step, but it depends on our human eyes to notice any difference. In addition there is also the spectral display, which shows signal strength at every frequency, over time. A spectral display would make the differences more obvious to the human eye.

* Although this is not a shortcoming in the test itself, the experiment apparently was done at only one sampling rate. If we were to test a variety of sampling rates, we would have a wider range of data to compare.

The sampling frequency is the most important factor which determines how accurately the original signal is preserved.

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As for the trigger level, I'm not sure what to make of that. I suppose it is the threshold of loudness which would cause a device to begin recording a sound, or would cause it to start digitizing a sound?