WIDEBAND SPEECH CODING STANDARDS AND WIRELESS SERVICES

WIDEBAND SPEECH CODING STANDARDS AND WIRELESS SERVICES
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宽带语音编码标准和无线服务

DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Kari Järvinen
Kari Järvinen
中科院分区：
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文献类型：
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作者：
Simão Ferraz;Kari Järvinen

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当今使用的大多数通信系统（例如公共交换电话网（PSTN））是基于窄带语音的，其中音频带宽被限制在大约200 - 3400 Hz。这种带宽限制可以追溯到大约世纪前有线电话的早期。当时，很难制造出价格低廉的高质量麦克风。此外，当电话通过很长的铜线时，较高的频率也会丢失。窄带语音至今仍被普遍使用。然而，对于某些场景，我们非常清楚其有限的质量。对于许多摩擦音和爆破音（例如/s/、/f/、/p/、/B/和/t/），大部分能量都在3000赫兹以上。由此导致的无法区分它们限制了窄带语音的可懂度。我们特别注意到这个问题时，试图捕捉未知的单词或名称通过电话。此外，当带宽被限制在窄带时，许多与说话者相关的特征消失了，这使得识别谁在说话变得更加困难。在电话里分辨母亲和女儿并不总是那么容易。在本专题中，术语宽带语音的使用遵循国际电信联盟（ITU）的定义，表示带宽与窄带电话相比大约增加了一倍的语音，其带宽范围约为50 - 7000 Hz。为了便于比较，所谓的超宽带扩展到14 kHz带宽，音频覆盖从20 Hz到20 kHz的完整可听频谱。
ost communication systems in use today, such as the public switched telephone network (PSTN), are based on narrowband speech in which the audio bandwidth is limited to about 200‐3400 Hz. This bandwidth limitation dates back to the early days of wireline telephony, around a century ago. At that time, it was difficult to build inexpensive highquality microphones. In addition, the higher frequencies were lost anyway as calls passed over long lengths of copper wire. Narrowband speech is still commonly used today. However, for certain scenarios we are well aware of its limited quality. For many fricatives and plosives (such as /s/, /f/, /p/, /b/, and /t/) most of the energy lies well above 3000 Hz. The resulting inability to distinguish between them limits the intelligibility of narrowband speech. We especially notice this problem when trying to capture unknown words or names over telephone. In addition, many speaker-dependent characteristics disappear when bandwidth is limited to narrowband, making it more difficult to recognize who is talking. Distinguishing a mother from her daughter is not always easy over the phone. In this feature topic the use of the term wideband speech follows the International Telecommunication Union (ITU) definition denoting speech where the bandwidth has been roughly doubled compared to narrowband telephony, with a resulting bandwidth in the range of approximately 50‐7000 Hz. For comparison purposes, the so-called super-wideband extends to 14 kHz bandwidth, and audio covers the full audible spectrum from 20 Hz to 20 kHz.