Audio Masking Effect – Part 6
When in practice it comes to the process of correcting a room to optimize the final sound and give it a certain color character or neutrality, it is absolutely necessary to determine the impulse characteristics of the desired room.
For this, measurements are made with a microphone at different points in space, and there is also an option to calculate the specified geometric dimensions of the room height / depth / width. The impulse response obtained as a result of calculations or measurements allows the room to be dynamically corrected (with sound-absorbing materials or materials that are reflected at certain points), as well as to affect the signal directly using filters or computer programs. In the case of a competent implementation of this method, it is quite possible to achieve a full three-dimensional surround sound effect at a given point in space. However, this assumes that the person will be at a specific point without turning their head. If not, a full recalculation and the entire procedure will need to be done again.
Fortunately, listening to music at home or in a car generally provides a more or less fixed position of the listener in space, allowing you to perform the necessary calculations and a one-time correction at an early stage of system construction. It is much more difficult to implement the correct sound for two or more listeners for the above reasons, but in this case it is possible to achieve an acceptable sound if you follow the technology described above. There is no doubt that in the end it is also necessary to take into account the final signal transformations that occur in the atrium and auditory canal, making corrections not only for the general model of auditory perception, but mainly for the individual characteristics of the hearing. structure. of each person’s auditory system.
Sound depending on the characteristics of the room
From the point of view of psychoacoustics, it is important to understand the great role that the room (or the volume at which you hear the sounds / music) has in the final character of the sound. As mentioned above, almost every feature in a listening room or car interior has a significant impact on the original sound signal, acting as a kind of filter. Such filtering introduces changes in the temporal structure and spectrum of the audio signal. Therefore, there are distortions and changes in the nature of sound originally inherent in the meaning of sound recording. These distortions can be analyzed and corrected to recreate the original sound image. In many ways, this is the core and most important foundation of modern “hi-fi” sound. It is important to remember that it is the characteristics of the volume at which listening to music takes place that has a fundamental effect on the sound or the music that a person listens to as a result. It is this understanding that avoids a host of mistakes often made by hi-fi enthusiasts striving to achieve the desired “reference” sound, ignoring this simple, but at the same time, the most important principle.
The sound image in the room, created by a conventional stereo pair, is made up of a series of processes and transformations that the sound wave undergoes from the moment the speaker is formed as a result of oscillatory activity until the moment it enters the room. ear canal. . What happens to the sound during this period? As you know, the sound wave generated by an acoustic system has a spherical shape. Consequently, the propagation of sound waves occurs in all directions from the emitting surface of the dynamic head. First, the listener usually perceives a direct wave, which can be represented by a “virtual” horizontal line clearly opposite the speaker. In addition, the rest of the waves come into action with a certain delay, which also reaches the listener’s ears. These waves often arrive already highly distorted and transformed, which happens as a result of multiple reflections from the surface of the listening room / volume boundaries. The degree of delay of the reflected waves in time in this case depends directly on the material of the surface of the walls / floor / ceiling, as well as the shape of the room and its size. After the image of numerous re-reflected waves has been formed, their number gradually increases, then the sound field gradually straightens, the distribution of sound energy in space flows evenly at all points, after which the image shifts toward a decrease.
