Psychoacoustic model

Peripheral auditory system

Psychoacoustic models are formed by modeling the ear structure of the peripheral auditory system and some psychoacoustic phenomena. The human peripheral auditory system is a system that preprocesses the signals sent to the auditory nerve. This system is mainly divided into three parts, namely, the outer ear, the middle ear and the inner ear. The outer ear is composed of the pinna and ear canal, which is the outermost part of the human auditory system. The main function of the outer ear is to collect sound energy and transmit it to the eardrum through the ear canal, and the external ear canal can also be used to protect the eardrum. The main role of the pinus is to reflect and attenuate sound waves, acting as an acoustic emitter and attenuator, and it can also help the brain identify the direction and location of the sound source. The inner ear is very close to the brain, and it can shorten the propagation time of action potentials.

Masking effect of sound

The human ear can hear very slight sounds in a very quiet environment, but in a noisy environment, these slight sounds are drowned out by the noise and the human ear cannot distinguish them. The presence of one sound makes the human auditory system not feel the presence of another sound. This phenomenon is called masking effect, that is, one sound acoustically masks another sound. The first sound is called the masked sound and the second sound is called the masked sound. Masking effects are further divided into: absolute masking, time domain masking and frequency domain masking. When the masking effect occurs, sounds with different properties such as pure tone and noise are generally used as masking sounds.

Absolute masking

The human auditory system itself also has the role of signal masking. The minimum value of pure tone that can be heard by the human ear in a quiet environment is called the absolute smell threshold. All the sounds below the absolute smell threshold will be masked, which is called the perfect masking.

Temporal masking

Temporal masking refers to the phenomenon that an audio signal with higher energy can mask the audio signal with lower energy appearing at the same time, before or after it. This masking phenomenon is also known as nonsimultaneous masking, which occurs when the masked sound and the masked sound arrive at different times. Temporal masking is further divided into lead masking and lag masking, masking the masking effect that occurs in a period of time before the sound is emitted, called lead masking.

According to relevant research, lead masking is only effective for a very short time, namely 20 milliseconds. When the masking sound has disappeared, that is, when it is no longer physically present, the masking effect still occurs, and this phenomenon is known as hysteresis masking. The intensity of lag masking decays exponentially with time until it becomes zero after 100 to 200ms.

Frequency domain masking

Simultaneous masking occurs when both the masked sound and the masked sound are present, a phenomenon known as frequency domain masking.

Haas effect

Haas effect, also known as the priority effect, when several sounds with the same sound pressure level are transmitted to the human ear at different times, the sound arriving first will mask the sound arriving later, and the human auditory system will judge the direction of the sound based on the sound heard first. This preconception auditory characteristic of the human ear is called Haas effect.

Your task

What is masking effect?

Share your thoughts and ideas in the comments below.