The exam includes stimuli at four different frequencies (500, 1000, 2000, and 4000 Hz) and white noise clicks of 50 ms duration. It is a useful test because it provides an index of auditory temporal resolution. In children, an overall gap detection threshold greater than 20 ms means they have failed and may have an auditory processing disorder based on abnormal perception of sound in the time domain. Gaps in Noise Test (GIN) also measures temporal resolution by testing the patients gap detection threshold in white noise. Pitch Patterns Sequence Test (PPT) and Duration Patterns Sequence Test (DPT) measure auditory pattern identification. The PPS has s series of three tones presented at either of two pitches (high or low). Meanwhile, the DPS has a series of three tones that vary in duration rather than pitch (long or short). Patients are then asked to describe the pattern of pitches presented. Masking Level Difference (MLD) at 500 Hz measures overlapping temporal processing, binaural processing, and low-redundancy by measuring the difference in threshold of an auditory stimulus when a masking noise is presented in and out of phase. The Staggered Spondaic Word Test (SSW) is one of the oldest tests for APD developed by Jack Katz. Although it has fallen into some disuse by audiologists as it is complicated to score, it is one of the quickest and most sensitive tests to determine APD. Modality-specificity and controversies
The issue of modality-specificity has led to considerable debate among experts in this field.
Characteristics
The American Speech-Language-Hearing Association state that children with (central) auditory processing disorder often:

have trouble paying attention to and remembering information presented orally, and may cope better with visually acquired information
have problems carrying out multi-step directions given orally; need to hear only one direction at a time
have poor listening skills
need more time to process information
have difficulty learning a new language
have difficulty understanding jokes, sarcasm, and learning songs or nursery rhymes
have language difficulties (e.g., they confuse syllable sequences and have problems developing vocabulary and understanding language)
have difficulty with reading, comprehension, spelling, and vocabularyAPD can manifest as problems determining the direction of sounds, difficulty perceiving differences between speech sounds and the sequencing of these sounds into meaningful words, confusing similar sounds such as "hat" with "bat", "there" with "where", etc. Fewer words may be perceived than were actually said, as there can be problems detecting the gaps between words, creating the sense that someone is speaking unfamiliar or nonsense words. In addition, it is common for APD to cause speech errors involving the distortion and substitution of consonant sounds. Those with APD may have problems relating what has been said with its meaning, despite obvious recognition that a word has been said, as well as repetition of the word. Background noise, such as the sound of a radio, television or a noisy bar can make it difficult to impossible to understand speech, since spoken words may sound distorted either into irrelevant words or words that dont exist, depending on the severity of the auditory processing disorder.