Digital Sound

Digital sounds better than analog. Its something like comparing the playback of a high end cassette tape to a compact disc. The three digital sound formats (SDDS, DTS, & SR-D) use different techniques to record and reproduce sound. All three formats sound exceptionally good.
If projectors were equipped to reproduce all three digital formats we'd simply look for a digital designation. Unfortunately, we experience incompatible digital formats. The decoder unit for DTS, SDDS, and SR-D gets attached to a projector. Only one sound format can be decoded at any time. Fortunately, film prints can contain code for all three digital sound formats but some don't.
If a movie only contains an SR-D soundtrack and is played through an SDDS equipped projector, the SDDS decoder gets no signal. All three digital formats employ an analog backup sound track. In the event that a digital decoder does not receive coherent information, it switches control to an analog decoder.
Many moviegoers have listened to a DTS only soundtrack in Dolby stereo because the projector could only decode SDDS! To avoid this, be sure to check if a movie has been digitally mastered with any format. Then check the box office and ask if the projector has been equipped to play that format. Its easy if the movie has all three digital sound formats. Just find a digitally equipped auditorium.

Dynamic range

the loudest to softest volume that a sound system can reproduce.

Frequency response

the highest (tweeter) and lowest (subwoofer) frequency sound that can be reproduced.

Compression ratio

lower ratios indicate less manipulation of digital sound information.

Usually theatres can reproduce 6 discrete sound tracks. That comes out to 5.1 sound channels due to the subwoofer. Five channels use full bandwidth audio (approximately 5-20,000Hz) while the 1 subwoofer channel has narrow frequency response (approximately 3-120Hz). Thus the bass track is considered on tenth of a channel. So 8 discrete tracks equal 7.1 sound channels.
SR-D and SDDS use acoustical masking techniques which analyze sounds that can be eliminated without any noticeable difference. Louder sounds overpowering quieter ones and anything beyond the range of human hearing gets edited out.

---



dynamic range 105db
frequency response 5-20,000Hz
compression ratio 5:1


1. Sony Dynamic Digital Sound reigns as the ultimate digital sound format. SDDS provides the best mix of dynamic range & frequency response due to bypassing the analog sound processor that all auditoriums come equipped with. Its an independent unit that routes signals directly to the amplifiers and speakers.
   Introduced in 1993 with the release of In the Line of Fire (September 1993) and Last Action Hero (July 1993), SDDS provides 100% data redundancy on digital information to help prevent digital signal dropout.
   SDDS utilizes 6 or 8 discrete sound tracks. Eight channel stereo creates separate signals for left surround, left, left center, center, right center, right, right surround, and the subwoofer. Its my recommendation to see a movie in SDDS if you can.
   

   ---

   

   dynamic range 96db
   frequency response 20-20,000Hz
   compression ratio 4:1
   

2. Digital Theater Systems utilizes 6 discrete sound tracks. The channels are left surround, left, center, right, right surround, and the subwoofer. Introduced in 1993 with the release of Jurassic Park (June 1993), DTS uses standard computer components, CD-ROM drives, and system software to maintain highly competitive prices.
   It can also be installed in theaters that SDDS & SRD (Dolby Digital) units wouldn't due to lenient sound requirements. Some theaters are equipped with DTS-S systems which are seriously inferior to DTS-6. DTS has promised to eventually upgrade these theaters.
   DTS prints a timecode track on the film print so that the CD-ROM and picture are synchronized. Each CD can hold up to 100 minutes of digital audio. Its the only sound format that doesn't encode the audio on the actual print.
   DTS offers lower dynamic range and frequency response than both SRD & SDDS. Its better than analog sound reproduction but continues to be my third pick in the digital category.
   

   ---

   

   dynamic range 120db
   frequency response 20-20,000Hz
   compression ratio 10:1
   

3. Dolby Digital Stereo encodes sound on the movie print. It uses 6 discrete sound tracks.
   All digital prints use an analog backup system. If the theater isn't equipped with a digital sound system, prints can still be played in analog sound. This design also protects sound playback if the digital unit fails.
   Dolby SRD switches to Dolby SR in the event of signal loss.