A Q band is a narrowly defined frequency interval that is selectively processed by a bandpass or notch filter. In hearing aids, Q bands are used to specifically amplify or attenuate specific speech or interference frequencies (e.g., tinnitus frequencies). The bandwidth of a Q-band is defined by the Q factor: the higher the Q factor, the narrower the band. Narrowband filters minimize unwanted effects on adjacent frequencies and allow for precise sound shaping. Adaptive hearing systems dynamically adjust Q-bands to changing listening situations to ensure optimal intelligibility.

The Q factor or quality factor of a filter describes the ratio of center frequency to bandwidth and quantifies the sharpness of the resonance. A high Q factor means a narrow bandwidth with steep edges and a pronounced resonance peak, while a low Q factor produces wider, flatter filter bands. In hearing aids, the Q factor is set for bell and notch filters to emphasize speech formants or suppress tinnitus frequencies. However, excessive Q values can cause phase distortion and sound artifacts. Fine-tuning the Q factor is part of hearing aid fitting to optimize naturalness and comfort.

Q-mapping is a method for representing spectral information in which the frequency spectrum is divided into bands with a constant Q factor. Unlike linear or octave-based analyses, Q bands adjust their width proportionally to the center frequency, enabling consistent relative resolution across the entire spectrum. In audiology, Q-mapping allows precise characterization of otoacoustic emissions and masking effects. It is also used in room acoustics to identify resonance modes and room modes. Software-based Q-mapping tools visualize complex spectral data in a clear and interactive way.

A Q-peak refers to the maximum resonance point within a narrowband filter or acoustic system. It marks the frequency at which the amplification or attenuation is strongest. In hearing aids, Q-peaks can cause unwanted sound coloration if resonance peaks are not carefully controlled. During filter calibration, the Q-peak is used to identify and reduce problematic resonances (e.g., housing reflections). In room acoustics, the analysis of Q-peaks reveals standing waves and room modes that can be reduced by sound-absorbing measures.

The Q value is a dimensionless parameter that describes the quality or efficiency of an element in various audio engineering contexts. In filter design, it corresponds to the quality factor (see Q factor), and in loudspeaker systems, it corresponds to the ratio of resonance frequency to bandwidth. A high Q value in loudspeakers indicates narrow bass resonances, which can lead to booming effects. In hearing aid development, the Q value is used in the evaluation of microphone designs and amplifier circuits. Consistent Q values are a prerequisite for reproducible sound quality and system stability.

Distressing noises are acoustic stimuli that are perceived as extremely disturbing or painful, such as drilling noises, shrill screeches, or sudden loud impulses. They often exceed the discomfort threshold and can contribute to stress reactions, auditory fatigue, and hyperacusis. In audiotherapy, such noises are specifically used in desensitization programs to gradually raise the tolerance threshold. Environmental and occupational safety guidelines define limit values to minimize distressing noises. Technical measures such as silencers, insulation, and active noise cancellation effectively reduce exposure.

Hearing quality encompasses objective parameters such as hearing threshold, dynamic range, and frequency resolution, as well as subjective aspects such as sound fidelity, comfort, and satisfaction. It is assessed using audiometric tests, questionnaires (e.g., SSQ scale), and everyday observations. High hearing quality enables precise speech comprehension, enjoyment of music, and reliable localization of sound sources. Hearing aid fitting aims to optimize all quality dimensions by fine-tuning filters, compression, and microphone modes. Regular follow-up checks and hearing training ensure sustainable hearing quality.

Cross-sensitivity refers to the influence of signals in adjacent bands on perception in a frequency band, such as masking effects. It occurs when filter-related slope steepness is insufficient and energy "spills over" into adjacent channels. In hearing aid development, filter qualities and slope steepness are selected to minimize crosstalk. Psychoacoustic tests measure masking level differences to determine individual crosstalk patterns. Fitting software takes this data into account to reduce overlap and improve speech intelligibility.

Cross-coupling describes interactions between auditory and vestibular systems, such as when loud sound stimuli trigger vestibular reflexes. Sound-induced vibrations can stimulate endolymphatic movements and cause nystagmus or nausea ("Tulio phenomenon"). This phenomenon is used in diagnostics to detect labyrinth fistulas or perilymph leaks. Avoiding extreme air pressure or sound peaks reduces unwanted vestibular reactions. Treatment focuses on vestibular rehabilitation to reduce cross-stimulation.

A quiet zone is an acoustically shielded area in which background noise is below the threshold of hearing, often used for sensitive audiometry or OAE measurements. It is achieved through sound insulation, decoupling, and active noise cancellation. In research, a quiet zone creates ideal conditions for precise psychoacoustic experiments. In clinical practice, quiet zones ensure reproducible hearing test results without environmental artifacts. Standards define maximum permissible background noise levels for quiet zones in medical facilities.

In audiology, "quotient" is often used for ratio values, such as SP/AP quotient in ECochG or speech reception quotient in speech intelligibility tests. The SP/AP quotient (summation potential/action potential) serves as a diagnostic marker for endolymphatic hydrops. A speech reception quotient indicates the ratio of correctly understood words to the total number and quantifies speech comprehension. Quotients enable standardized comparisons between patients and measurements. They are an integral part of diagnostic reports and care decisions.