THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

19.2 Recording Equipment 575CD 0.7 GB DVD 4.7 GB Blu-ray Disc 25 GB1.6 μmPit Length0.74 μm0.32μmTrack Pitch: 1.8 micronMinimum Pit Length: 0.8 μmStorage Density: 0.0636 GB/cm 2Track Pitch: 0.74 micronMinimum Pit Length: 0.4 μmStorage Density: 0.429 GB/cm 2Track pitch: 0.32 micronMinimum Pit Length: 0.15μmStorage Density: 2.283 GB/cm 2Figure 19.2. Data layers in 0.7 GB CD disk, 4.7 GB DVD disk, and 25 GB Blu-ray disk.Note the pit lengths generally decrease with increasing disk capacities.light, hence yielding smaller data areas and more densely packed data deliveringhigh capacity. The Blu-ray is a Sony development that holds 25 GB in singlelayerformat, but will have two layers and a double-sided recording holding asmuch as 100 GB. Such capacities can hold high-definition movies and in theaudio mode could presumably easily contain the entire Wagner’s Ring Cycle. Itneeds a hard coating to protect it and requires a special player. The HD-DVD,also intended for playback of high-definition movies, features a 20-GB capacitybut could possibly be expanded to 50 GB via multiple layers. The HD-DVD doesnot require a protective cartridge or coating but it also does require a specialplayer. Figure 19.2 compares the data layers of the 0.7-GB CD, the 4.7-GB DVD,and the 25-GB Blu-ray disks. As of this writing, there is a formidable conflictraging as to which of these two high-definition formats will gain ascendancy. Somemovie studios and developers (NEC and Toshiba) have advocated HD-DVD; otherstudios, major computers manufacturers (Dell and Hewlett Packard), and the BlurayDisc Founders (Sony, Philips, LG, Matsushita, Pioneer, Samsung, Sharp, andThomson) are boosting Blu-ray.Voice RecognitionVoice or speech recognition is the ability of a machine or device to receive andinterpret dictation or to comprehend and carry out oral commands. In use withcomputers, analog audio must be converted into digital signals through an analogto-digital(A/D) converter. In order that it can decipher the signal, a computer musthave a digital database, or vocabulary, of words or syllables, and a rapid meansof comparing this data with signals in the format of speech patterns stored in thehard drive and loaded into memory when the program is operating. A comparatorcompares these stored patterns against the output of the A/D converter. Thus, theprogram’s vocabulary constitutes a recording of sorts.