Fundamentals of Audio Production, Chapter Fundamentals of Audio Production Chapter Eleven: Transporting Sounds

Fundamentals of Audio Production, Chapter 11 2 Transporting Audio The method by which audio will be delivered to the consumer will determine how the content should be prepared. It is important to understand the limitations and capabilities of the various means of transporting audio.

Fundamentals of Audio Production, Chapter Copper wire technology Telephone circuits using a single pair of copper wires carried early radio signals AM radio bandwidths of 5 KHz Vacuum tube amplifiers or “repeaters” boosted the signals “Twisted pair” copper wire still provides much of the backbone for telephone transmission

Fundamentals of Audio Production, Chapter Copper wire technology Technological advances now permit twisted pairs to carry broadband audio Twisted pair also carries broadband data and video signals “Coaxial” cable introduced in the late 1930s allowed even greater bandwidth Coaxial cable became the standard for television signal distribution

Fundamentals of Audio Production, Chapter Copper wire technology

Fundamentals of Audio Production, Chapter Microwave technology Named for the extremely short wavelengths of Radio Frequencies used for transmission Microwaves travel only in straight lines Transmitted and received using tightly focused parabolic dishes Make use of relay stations

Fundamentals of Audio Production, Chapter Microwave technology

Fundamentals of Audio Production, Chapter Microwave technology Capable of travelling great distances – up to 40 miles Capable of extremely large bandwidths and high data rates

Fundamentals of Audio Production, Chapter Satellite technology Communication satellites orbit 22,300 miles above the equator Communication satellites orbit the earth once every 24 hours –They are synchronized with the earth’s orbit –Called “geosynchronous” orbit Satellites appear suspended above a point on earth –Appear “geostationary”

Fundamentals of Audio Production, Chapter 11 10Fundamentals of Audio Production, Chapter Satellite technology Satellites vary according to power and RF band they utilize Low power lower frequency satellites are called “C-band” High power higher frequency satellites are called “Ku-band” “Transponders” receive signals from earth stations and re-transmit to earth’s surface

Fundamentals of Audio Production, Chapter 11 11Fundamentals of Audio Production, Chapter Satellite technology Satellite radio services use the S-band and F-band segments of the spectrum to transmit multiplexed signals to subscribers

Fundamentals of Audio Production, Chapter 11 12Fundamentals of Audio Production, Chapter Satellite and Microwave A transmission system using microwave, satellite, copper and optical fiber

Fundamentals of Audio Production, Chapter 11 13Fundamentals of Audio Production, Chapter Optical fiber technology Optical fiber is made from highly purified optical glass The glass is drawn into a single continuous strand with the diameter of a human hair Fiber optics use “total internal reflection” to reduce attentuation The glass stand is wrapped in “cladding” that reflects the light internally

Fundamentals of Audio Production, Chapter 11 14Fundamentals of Audio Production, Chapter Optical fiber technology Optical fiber cladding produces “total internal reflection”

Fundamentals of Audio Production, Chapter 11 15Fundamentals of Audio Production, Chapter Optical fiber technology EIAJ OPTICAL CONNECTOR

Fundamentals of Audio Production, Chapter 11 16Fundamentals of Audio Production, Chapter Digital wired technology Integrated services digital network or ISDN developed in the 1980s, offers digital transmission over the telephone network ISDN terminals convert analog to digital, and vice-versa ISDN signals are exchanged between terminals – not over the Internet The bandwidth of ISDN allows CD quality digital signals to be transmitted in real time

Fundamentals of Audio Production, Chapter 11 17Fundamentals of Audio Production, Chapter Internet based technology Audio files can be transferred over the Internet using the same telephone network previously described Files may transferred two ways –As complete files – like any other data file –As a stream – with data transferred continuously in near-real time

Fundamentals of Audio Production, Chapter 11 18Fundamentals of Audio Production, Chapter Internet based technology Coder-decoder (CODEC) software is used to compress audio files for Internet transfer Lower compression rates yield better bandwidth and dynamic range 1:1 compression is called “lossless” compression – preferred by audio professionals

Fundamentals of Audio Production, Chapter 11 19Fundamentals of Audio Production, Chapter Internet based technology Two CODECs that support 1:1 compression are “AIFF” and “WAV” Higher compression ratios yield smaller files and faster transfers “Lossier” formats use compression ratios from 4:1 (MPEG1) to 53:1 (VOX)

Fundamentals of Audio Production, Chapter 11 20Fundamentals of Audio Production, Chapter Internet based technology Streaming audio is sent continuously and played immediately as received Streaming software includes “buffers” which store data for a short time before playback Buffering avoids start and stop of the audio stream due to network traffic

Fundamentals of Audio Production, Chapter 11 21Fundamentals of Audio Production, Chapter Internet based technology “Podcasting” –MP3 files distributed over the web –Uploaded to and downloaded from servers –Sent as s –“Podcatchers” may use RSS aggregator software to receive new content automatically –Still subject to copyright and music licensing regulation

Fundamentals of Audio Production, Chapter 11 22Fundamentals of Audio Production, Chapter Broadcast technology Audio may be transferred long distances using radio frequency broadcasting The radio frequency signal is modulated Modulation superimposes the analog signal on the radio frequency carrier

Fundamentals of Audio Production, Chapter Amplitude modulation –The amplitude or strength of the carrier is altered by the amplitude of the audio signal Fundamentals of Audio Production, Chapter Broadcast technology

Fundamentals of Audio Production, Chapter 11 24Fundamentals of Audio Production, Chapter 11 Broadcast technology Frequency modulation –The frequency of the carrier is altered by the amplitude of the audio signal

Fundamentals of Audio Production, Chapter 11 25Fundamentals of Audio Production, Chapter Broadcast technology It is possible to transmit audio by radio in digital form Digital broadcasting has low distortion, excellent signal-to-noise ratio, and no signal degradation