5.8 Other Spatial Effects
5.8.1 Digital Versions of Classic Reverbs
In the past, before the era of digital signal processing, many systems were used to create a reverberation effect. In studios the common way was to replay the recorded signals in a reverberant room or a corridor and record it again in that particular space. In addition, plates and springs were applied to create a decaying tail to the sound. Recently, researchers have modeled the physical principles of old-school reverberators and they have proposed digital implementations of them. For example, plate reverbs have been implemented with finite difference schemes [BAC06, Bil07]. An extension to digital plate reverbs to handle objects of any shape has been made with modal synthesis methods. Thus, simulations of the vibration of many different shapes and materials can be performed in real time [Max07]. Spring reverbs have also been modeled and it seems that efficient implementation can be achieved with parallel waveguides, which include dispersive all pass filters [ABCS06].
5.8.2 Distance Effects
In digital audio effects, the control of apparent distance can be effectively introduced even in monophonic audio systems. In fact, the impression of distance of a sound source is largely controllable by insertion of artificial wall reflections or reverberant room responses.
There are not reliable cues for distance in anechoic or open spaces. Familiarity with the sound source can provide distance cues related with air absorption ...