5.1聲道音響撥放系統之多頻帶空間響應模擬器

Abstract

摘要 最早的多聲道撥放系統格式是針對電影院的撥放於1950s由杜比實驗室所提出。其與一般的Stereo(2或3聲道撥放系統)的主要差異在於Surround Sound增設。其主要是為了增加聽者聆聽的臨場感，產生包圍性以及空間的效果，而不在於定位。 現今不論在軟體或者硬體上有許多的聲道分離技術，其中有些都是利用簡單的濾波器(低通/高通/帶通濾波器)來達成聲道的分離，但是這樣的方式非常的粗略並不精確。為了要得到比較正確的分離方式，在本論文中我們參考Dolby Surround 解碼的觀念，而主要專注於空間響應的模擬。根據杜比實驗室Surround sound的定義，我們藉由空間響應模擬器產生不同品質的audio 訊號，然後將這樣的傳統stereo訊號用一modified Dolby Surround decoder進一步的擴展成5.1聲道撥放。我們更進一步的要求聲音品質的變化，所以我們引進不同空間大小有不同脈衝響應的概念，以及利用一個多帶等化器來產生不同感覺的聆聽效果於多聲道的撥放系統。如此便可以得到一個豐富且附有臨場感的聆聽經驗。

Abstract The earliest multichannel reproduction system format was brought up for theatre by Dolby Liboratories Inc in 1950s. The main difference between the conventional stereo (two or three dimension) and multichannel sound system is the setup of surround sound channel. The main purpose of surround channel is to produce the effect of liveness, sense of envelopment, and wide spatiality. There exist many methods for audio channel separation in nowaday’s hardware and software techniques. Most of them used simple filters (low/high/band pass) to reach channel separation, but this kind of method is quite rough. In order to get a correct separation solution, we use the concept of Dolby Surround decoding in our research. In this thesis, what we engaged is about room effect simulation. Based on the definition of surround sound referred to Dolby Liboratories Inc., we generate different quality of audio sound sources by a room effect emulator, and then turn the conventional stereo into 5.1 channel sound system by a modified Dolby Surround decoder. We further introduce the concept of room effect impulse response in different room-dimension, and use multi-bands equalizer to generate many kinds of music impression for the multichannel sound system. In this way, we can get a full and a live listening experience.