The categorization and identification of previously ignored visual or auditory stimuli is typically slowed down—a phenomenon that has been called the negative priming effect and can be explained by the episodic retrieval of response-inadequate prime information and/or an inhibitory model. A similar after-effect has been found in visuospatial tasks: participants are slowed down in localizing a visual stimulus that appears at a previously ignored location. In the auditory modality, however, such an after-effect of ignoring a sound at a specific location has never been reported. Instead, participants are impaired in their localization performance when the sound at the previously ignored location changes identity, a finding which is compatible with the so-called feature-mismatch hypothesis. Here, we describe the properties of auditory spatial in contrast to visuospatial negative priming and report two experiments that specify the nature of this auditory after-effect. Experiment 1 shows that the detection of identity-location mismatches is a genuinely auditory phenomenon that can be replicated even when the sound sources are invisible. Experiment 2 reveals that the detection of sound-identity mismatches in the probe depends on the processing demands in the prime. This finding implies that the localization of irrelevant sound sources is not the inevitable consequence of processing the auditory prime scenario but depends on the difficulty of the target search process among distractor sounds.