A new technique has been developed for precisely quantifying the temporal contrasts that exist between two sound samples. This technique is based on envelope subtraction, and generates an Envelope Difference Index that may be used t o help clariQ whether alteration of the natural speech envelope via amplification improves or degrades speech intelligibility. The Envelope Difference Index method may also be used t o assess hearing aid saturation, and may have other applications as well. The technique is applicable whenever a precise quantifwation of the difference between two temporal envelopes is required, regardless of stimulus duration. (Ear & Hearing 1994;15:93-99)

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Hyperacusis, as defined here, is a relatively rare condition in which the patient, with or without hearing loss, experiences severe loudness discomfort to everyday environmental sound levels. The case studies of 14 patients with severe hyperacusis are described; all wore passive attenuators (earplugs and/or earmuffs) in an attempt to alleviate their discomfort, frequently producing communication difficulties. These subjects were fitted binaurally with experimental electronic loudness suppression devices housed in in-the-ear casings. The devices supplied low-level amplification followed by an extreme form of amplitude compression for moderate or high-level inputs in an attempt to reduce loudness discomfort without reducing audibility. Many of the subjects were found to function with a wider dynamic range with the active devices compared with passive attenuators or the unoccluded ear, and most reported that they benefited from the devices in at least some listening situations.