Your PC acts like an oscilloscope or FFT(spectrum) analyzer by this Windows application!! (Freeware) You can input signals via microphone and check the time/frequency domain wave. Let's try this one before you purchase expensive equipments!! System requirement is following. Sound card needs to be full-duplex type, which accepts recording and playing concurrently. Microphone and speakers are connected to the card. DirectX Runtime is installed. See following site to download. Windows 98 Windows Me Windows 2000 : DirectX 9.0a Windows 95 : DirectX 8.0a Windows XP already includes DirectX. Windows NT is out of support. Download "Software Oscilloscope". (SftOsc.exe : 432kBytes) An example of time-domain wave. You can measure the time scale and magnitude. An example of frequency-domain wave. You can analyze the spectrum. Please input signals from PC's microphone, then concurrently the sound can be heard from speakers!! The sampling frequency is 11k, 22k or 44kHz. Please give me what you think about "Software oscilloscope". Download "Software Oscilloscope". (SftOsc.exe : 432kBytes) Updated on 19 July, 2004 (ver 1.2). See "Bug Information" for detail.