X‐ray spectra were recorded with a notebook computer and analyzed by software on the computer, without a pulse height analyzer (PHA) or a digital signal processor (DSP). An audio (microphone or line) input on a personal computer has a built‐in analogue‐to‐digital converter (ADC) for digital audio recording. The output signal of the X‐ray detector is recorded through the audio input of the computer and then analyzed by software on the computer. On the basis of this method, X‐rays from a radium source were measured with a cadmium telluride detector. K X‐rays of bismuth were detected. Full width at half maximum (FWHM) was 5.6 keV at Kα of bismuth (77.1 keV), enough to separate Kβ (87.3 keV) from Kα of bismuth. The present method achieved almost equal energy resolution as that of the regular method (5.3 keV FWHM at 77.1 keV). Copyright © 2010 John Wiley & Sons, Ltd.