Suppressed sound

Hi . . . welcome to the forum !
So, it sounds like you are using the laptop onboard soundcard for recording ?
If you don't have a separate audio interface, you might get unexpected problems like this recording to a DAW such as Sonar. Most modern computers come with sound cards already built into the motherboard and are referred to as Integrated Sound Cards or Onboard Sound. Dedicated sound cards, the opposite of integrated, can be installed onto the system and are more convenient for professional audio recording.
 
Also, do you know what type of audio drivers are set up in Sonar preferences ? eg. Asio, WDM, MME, Wasapi

Noynekker / Kalle Rantaaho:
Thank you for your responses.
Noynekker, I am only using the built in sound card that came with my laptop.
I looked at the Audio options tab on my SONAR program and see that it has the options for WDM, WASAPI, ASIO & MME.
It is currently set at MME (32bit). Would changing it to one of the other's make a difference?
 
Kalle Rantaaho, I am basically playing a song on one laptop computer and recording it to a second laptop; using only
a 1/8in line jack to directly connect both computers. I haven't tried recording instruments or using a mic.
I did try playing back the recording on another external device (small sound system) and it was still the same.
 
The best way to describe what I mean by suppressed sound is that the playback sounds like a "wave" that goes from fairly
clear sound down to a low muffled sound, then back up to a clear sound, continuing that way throughout the entire playback.
Any suggestions? 

It sounds like you are saying the music is loud when it is loud but too soft when it is soft. At least that is the way I would take:
"The playback sounds good when the music dynamics are strong but it tends to "suppress" when the music is soft."
 
If that is the case, then the problem is just low signal at those points. If the signal drops below what it takes to drive your speaker/headphone into the audible range you will get cutoff. Your meters should confirm that, and upping the gain on playback should make it less "suppressed," although it will likely make the normal part too loud. Ideally you should look into why the difference between the normal and soft/suppressed (dynamic range) is so large when you are recording in the first place. A compressor plugin can reduce the loud parts so that they will not clip or break your ears or speakers while you increase the gain to raise the soft parts relative output volume.
 
Note that there is a big difference between how loud music sounds on playback (the volume) and how it is recorded, which for want of a better word is saturation. Volume of even very "soft" recording can be amplified on playback, although with some potential for distortion. Music that is recorded with peaks near the zero dB on your SONAR meters is fully saturated, it has digital data that is nearly as many bits as you can accurately represent. Parts of the recording that drop too many bits/dB below the peaks will present a problem like you describe. If you try to raise the saturation level on the recording to bring the relative soft parts up, you are likely to raise the peaks above what digital data can represent (clipping or digital over). That will definitely cause some very nasty distortion. That is the problem a compressor is designed to handle by effectively subtracting more bits from the louder parts relative to the softer parts.