I have ordered the parts and the parts have arrived. I have got a piezo electric sensor. I have also got an Arduino, ATMega8 and an LM386 op-amp. I am now experimenting with these to see which is most appropriate. The Arduino uses just a USB port for communications and power while the LM386 uses the audio jack for an output. The ATMega8 can be interfaced with a serial interface this can then be converted to a usb interface. The LM386 also requires a seperate power supply. On the other hand, an Arduino costs US$29 while the LM386 cost 1RMB(US$0.12) and the ATMega8 cost 8RMB(US$0.96). Overall the LM386 is most cost effective. On the other hand the ATMega8 does not cost so much and can be neatly interfaced with a serial interface. The ATMega 8 can also be programmed to analyze the pulse on the spot.