Impact sounds are occasionally generated by the attachments (e.g., a punching system and document feeders) of office equipment (e.g., multifunction peripherals) in addition to the body of the office equipment generating noise and thus affect the equipment's sound quality. To investigate the effects of acoustic characteristics of the impact sounds of attachments on the perceived impulsiveness of the noise emitted by multifunction peripherals, psychoacoustical experiments were carried out using synthesized operating noise including impact sounds of attachments in which the spectral features, the degree of salience of the impact sounds and the cycle duration between sounds were systematically varied. The results revealed that impressions of impulsiveness increased as the energy of high-frequency components increased and the cycle duration became shorter. The perceived impulsiveness was highly correlated with an acoustic measure of the fifth percentile of the sound pressure level (LA5), which was also correlated with a similar impression in a previous study. Logistic regression analysis, in which the relationship between the proportions of participants who evaluated the stimuli as bothersome and LA5 was investigated, revealed that LA5 values of stimuli that were evaluated as being bothersome by more than half the participants were around 50 dB.