Sound Card Oscilloscope is a dual-channel oscilloscope created by Virtins Technology that lets you perform advanced sound analyses. Unlike most sound oscilloscopes, this multimedia software does not search for trigger events after data collection, and instead uses a specially-designed data acquisition approach. With this, it can monitor the input signal continuously without missing any trigger event before the frame of data is collected. As a result, the app has a very fast screen refresh rate and a truly real-time response.  Moreover, it relies on a sophisticated triggering method, including pre-trigger and post-trigger, which are typically missing from other sound card-based instruments. The app has got all the features found in modern digital storage oscilloscopes, making it a great audio software. It comes with a configurable interface with loads of options. However, the registration process can be complicated, and the interface is a bit cramped. But if you want a powerful PC-based virtual instrument, this app is one of your better bets.