Glossary

When talking about hyperacusis, it becomes inevitable to use certain terms related to acoustic physics or simply auditory medicine. For those who are unfamiliar with the meaning of words such as frequency, bandwidth, octave, etc., I will explain here exactly what all those terms mean in order to facilitate the understanding of the articles hosted on this blog.

• Frequency spectrum analysis. This is the graphical representation of the frequencies and their intensity that make up a sound of a given duration.
• Bandwidth. The bandwidth of a sound is the range of frequencies it contains. If the range is wide, it is called wideband, while narrowband refers to small bandwidths.
• Attenuation. This is the decrease in the intensity of a sound.
• Octave band. This is the bandwidth whose distance between the lower and upper limit is one octave. Therefore, octave bands are bandwidths of 1,000–2,000 Hz, 4,000–8,000 Hz, 440–880 Hz, etc.
• Frequency. The frequency of a sound is the number of vibrations per second and is expressed in hertz (Hz). If the frequency is low, we talk about low frequencies, while if it is high, we talk about high frequencies. The human ear only hears from 20 Hz to 20,000 Hz. Low frequencies range from 20 Hz to 250 Hz. Mid frequencies range from 250 Hz to 2,000 Hz. And finally, high frequencies are those ranging from 2,000 Hz to 20,000 Hz.
• Intensity. The amplitude of the vibration, that is, the path travelled by the molecules of the medium while vibrating, is what is known as intensity. It is expressed in decibels (dB). The greater the amplitude, the greater the intensity.
• Octave. The octave of a frequency is double that frequency. Thus, the octave of 1,000 Hz is 2,000 Hz.
• Limbic system. This is the system that triggers physiological responses based on emotions (such as anger or fear) and is also related to learning and memory.
• Autonomic nervous system. This is the system responsible for controlling involuntary actions such as heart rate, sweating, arousal or muscle tension.
• Sound. Sound is the propagation of the vibrations of the molecules of a medium (gaseous, liquid or solid) that end up stimulating our ears and thus producing the perception of sound. The main characteristics that define a sound are frequency and intensity.
• Loudness. This is the sensation of intensity perceived by the brain, which is not the same at all frequencies. The human ear is more sensitive to the bandwidth of 500–8,000 Hz. For the rest of the frequencies, a greater intensity is required to be perceived at the same volume.
• Pure tone. Sound composed of a single frequency.
• Hearing threshold. This is the minimum intensity required for a sound to be perceived by the ear.
• Pain threshold. This is the minimum intensity from which sounds cause pain. The pain threshold in humans is around 120 dB.