infrasound are difficult to analyse with a standard equipement. Generally you can find infrasound generated by an engine or by a natural phenomenom. I have tested the measurement with the sound card of my computer line attached to a wire placed on the ground or on an engine. With a free sofware such as audacity you are able to extract some intersting information.

infrasound mesurements are made by seismo sensors-diapason 0-20Hz produser was "Vibropribor" Taganrog (Rus). The last mesurements on foundation were made by accelerometers manufactured Wilcoxon Research(USA) ,recorder Sony 8-channel digital data recorder. In some cases is usefull one channel data collector-analyserCMVA55 and vibrosensor from SKF Cndition Monitoring(  USA).Low frequancy high sensitivity sensorsand any vibro table for research-they are standart equipment

What is your band requirement ?

What is the medium (air, water ...) ?

You can take a look to Bruel & Kjaer products, they are expensive but they are viewed by many as the best transducers (at least in my field, underwater acoustic).

For the acquisition device, poor chance a sound card (even a high-grade one) can do the job because they won't pass DC to 20Hz, 50Hz or 100Hz. The lowest I've found are from the RME brand, they are  advertising 5Hz at -3dB , and i've measured mine wich cuts at 1 or 2Hz.

That said, another culprit of doing acquisition with a sound board is if you need to synchronize the start of the recording session (no trigger input).

The answers to your question strongly depends on what you want to do in terms of recording (or generating) infrasound. It depends on the frequencies and sources of infrasound you want to consider, the distance to your sources, the medium (air, water ...), the accuracy you aim at and the goals of your study.

For infrasound measurement at frequencies of let's say 1-20 Hz, you can use specialized microphones, e.g. by Bruel&Kjaer. For interests in frequencies way below 1 Hz you should use microbarometers, that are specialized to recordings at frequencies of 0.1 to 10 Hz. MB2000, MB2005, MB3, Chaparral Physics 25 or 50 are models often used in infrasound Monitoring contexts. A/D converters are integrated in the newest of these or have to be added as separate digitizers (with Sound cards having only limited capabilities here, yes).

For infrasound generation, you have to construct your own device, since you need a good subwoofer and a large air volume (the size of a room or container) to generate these very low, infrasonic frequencies with accordingly large wavelengths.     

This is all quite complex and expensive equipment in the range of k€'s, so it certainly depends on what your resources and goals are.

InfraSound Detector for android smartphone. You can measure a frenquency