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Sound Created @October 14, 2022 9:32 AM Course Multimediální technologie Procedure Related - Incoming Related - Outgoing Status Open Summary: Sound vibrations...

Sound Created @October 14, 2022 9:32 AM Course Multimediální technologie Procedure Related - Incoming Related - Outgoing Status Open Summary: Sound vibrations progating acoustic wave mainly airwaves captured and processed by auditory system approx. 340 m/s in air multiples of speed of sound = Mac Number - M Acoustics branch of science studying sound founded by Pythagoras it studies the origin, propagation, perception of sound - psychoacoustics branches of acoustics: physics - the origin and propagation music - sounds and their combination Sound 1  linguistics - pronunciation physiology - origin of sound in vocal cords construction - how to improve/limit sound propagation inside electroacoustics - recording, playback and transmission of sound by using electricity Frequency hearing range is approx. 20 - 20 000 Hz infrasound < 16 Hz ultrasound > 20 kHz Wave Propagation oscilation orientation longitudinal - oscilation on the plane of wave propagation direction the vibration is parallel to the direction the wave travels particles oscilate on the same plane as the wave - compression and rarefaction wave is the change in pressure - undisturbed vs maximum only the wave moves, particles oscilate transverse - oscilation perpedicular to the plane of wave propagation direction only the wave moves, particles oscilate particles oscilate perpedicularly to the direction of propagation shaking dust off a doormat light propagation Sound 2  wave propagation traveling - wave travels standing - wave vibrates it vibrates on the same spot node - zero displacement anti-node - maximum displacement static amplitude - each point longitudinal - wind istruments transverse - string instruments Phase, Wave Interference in a phase - it has the same amplitude at the time t odd multiple of π (180 degrees) - opposite phase, waves cancel each other out even multiple of π (0 and 360 degress) - in phase, waves are summed Sound 3  different shift of phase - waves add and subtract in closed space, the sound is reflected - gets stronger/weaker Huygens-Fresnel Principle - Sound Propagation = sound propagates to all directions, with the same speed - spherical wavefront every point on a wavefront is itself the source of spherical wavelets and the secondary wavelets emanating from different points mutually interfere wavefront - set of point oscilating in phase sound is reflected, diffracted, aborbed similarly as other waves Doppler Effect = change of frequency and wavelenght of received signal in comparison to the original, caused of non-zero relative speed between the source and receiver the change in frequency of a wave in relation to an observer who is moving relative to the wave source 1842 - Christian Doppler any waves - light (redshift, blueshift) Types of Soundwaves sine, square, triangle, sawtooth Sound 4  Acoustic Pressure power increases with square of pressure - reason for second power instead of 10×logxy we use this: 20×logxy expresses intensity of sound - e.g. rock concert or dormitory party Lp = 0 dBSPL = 0.00002 Pa - absolute threshold of hearing Lp = 94 dBSPL = 1 Pa - reference value for measurements of microphone sensitivity Lp=120 dBSPL = 20 Pa - very loud, may cause pain Lp=130 dBSPL = 63.2 Pa- threshold of pain (varies with frequency, age) Lp=194 dBSPL = 1 atm - the loudest undistorted sound, when higher - vacuum between waves index SPL (sound pressure level), m, u, V and other give absolute dimension to decibel, bacause they state the reference value Types of DBS dBSdBFS - Full Scale negative values with maximum 0 dBFS = ratio between the played signal and highest signal in specific digital device before distorsion - clipping dBdBu - reference value 0.775 VM0.775 VRMS dBdBV - reference value 1 VM1 VRMS dBdBm - reference value 1 mVM1 mVRMS SOL - Standard Operating Level: - line-level +4 dB - professional, −10 dB consumer level equipment Beats an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies Sound 5  final f is the average, speed of changes in volume = the difference f binaural beats - different sine wave in each ear - not a physical interference but processing in medulla oblongata DAW Digital Audio Workstation Mac or a real computer with proffesional sound card and other HW Pro Tools, Logic, Cubase, Nuendo, Ableton, GarageBand FOSS - Ardour, Radium, Audacity, Luppp, JAMin, Frinika you will use Avid Pro Tools - Windows/macOS HW Pro Tools HDX and HD products Binaural Hearing = Human Hearing thanks to the difference in time which sound arrives to left or right ear, brain can guesstimate the direction of the source the most sensitive is the perception of mid to high frequencies bass, i.e. low frequencies are not percieved as well equal-loudness contours - ISO 226:2003 Monophonic, Stereophonic and Quadraphonic Sound mono = single source, channel - it does not matter how many loudspeakers we have stereo = two or more loudspeakers, Channels can create an illusion that sound comes from anywhere on the axis between 2 loudspeakers phantom centre - an imaginary source of sound between 2 loudspeakers Sound 6  FM radio was created because of stereo, recording media had to be upgraded quad = four channels, four loudspeakers mainly in 70’s, comercial flop, technically difficult Audio Signal electronic representation of sound, changes in voltage achieved by tranformation of mechanical motion to changes of voltage - kinetic to electric energy we get a sound with reversed process electroacoustic transducer = microphone and speaker audio signal flow is the path and audio takes from source to output earlier only analog - manipulation with paramters of electricity digital sound requires Analog-to-digital and Digital-to- analog converters sound is converted from air movements to electricity, to bits and back Analog Sound Recording since the end of 19th century mechanical wave is converted to voltage that is recorded as a groove or electro-magnetic track quality also depends on the speed of medium - the faster, the better higher level of noise, additional noise from dirt gramophone records, tapes, discs difficult to copy - degradation, wow, flutter Dolby B, C, S, HX and CX, DBX - technology for the noise reduction but reducing compatibility Sound 7  Gramophone Record 1877 - phonograph cylinder - Thomas Alva Edison 1888 - shellac record - Emile Berliner originally mono, since 50’ from Polyvinyl chloride with stereo stero track - Westrex system 45/45 diameter either 7”, 10” or 12” with 33, 45 or 78 rpm speed single approx 4.5 min, LP 22 min on a single side records are pressed from metal master, which is carved out GZ Media in Lodenice - largest producer in the world - 25 million records annually, 25 % of the production Gramophone originally fully mechanical - clockwork with funnel it works similarly to the microphone stylus oscilates and generates a proportional electrical voltage in coils usually needs preamplifier an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise- tolerant and strong enough for further processing cheap gramophones are destroyin record, decent gramophone costs ten/twenty + thousand CZK Digital Audio analog signal must be digitized - converted to 1s and 0s AD and DA converters continuous function to discrete values low quality converters in cheap or small devices, better in receivers, sound cards Sound 8  # of A/D-D/A converions must be minimum, one ideally the advantage is lossless copying, easy editing LPCM - linear pulse-code modulation PDM - pulse-density modulation LPCM PCM = linear pulse-code modulation specific amplitude values are encoded into codewords of pulses of different weight 1937 - Alec Reeves the quantization levels are linearly uniform most common format of digital sound sampling measuring the voltage X-times per second and recording the value into Y-bits X = sampling frequency, Y = bit-depth the higher the frequency and bit-depth, but more than 44.1 kHz for playback is nonsense HD audio is fake news and scam bit-depth determines dynamic range and sample precision 41+ kHz makes sense for recording, postproduction etc. PDM relative density of the pulses corresponds to the analog signal’s amplitude marketed by Sony as DSD - Direct Stream Digital Super Audio CD or online shops with HD audio -.dsf or.dff only 1-bit depth, but sampling frequency is 2.8224 MHz or more frequency denoted in multiples of CD sampling frequency - DSD 64, 128, 256, 512 Sound 9  not compatible with LPCM, neccessary to have special D/A converter or convert to LPCM mainly to be found in mancaves of audiophiles Clipping if part of signal is too powerful, >0dBFS, A/D converter hits the wall and cannot convert it audio signal is distorted, ugly power of signal can damage devices in audio signal flow or the listener Compact Disc Digital Audio 1982 - Philips and Sony stereo LPCM 44.1 kHZ, 16-bit not CD-ROM - different format by Denon it uses the infrared laser with … it is made of polycarbonate and aluminium, data are under the artwork diameter enables also text - CD-Text, simple graphics - CD+G and CD+EG Other physical digital media 1987 - DAT - Digital Audio Tape - Sony - stereo, up to 48 kHz, 16-bit, 3 hours 1992 - DCC - Digital Compact Cassette - Philips and Matsushita - similar only lossy, 2 hours 1992 - MiniDisc Sony - ATRAC or LPCM - used in DJing, known from music video Freestyler, Matrix or Demolition Man movies Sound 10  DVD-Audio - LPCM or MLP: stereo up to 192 kHz, 5.1 up to 96 kHz, 24-bit High Fidelity Pure Audio - Blu-Ray stereo PCM 192 kHz, surround Dolby TrueHD, DTS-HD MA, Auro-3D 96 kHz, 24-bit Format types UNCOMPRESSED AUDIO FORMATS WAV, AIFF, AU or RAW header-less PCM LOSSLESS COMPRESSION FLAC, Monkey’s Audio (.ape), WavPack (.wv), TTA, ATRAC, ALAC (.m4a), MPEG-4 SLS, MPEG-4 ALS, MPEG-4 DST, Windowds Media Audio Lossless (WMA Lossless), Shorten (SHN) LOSSY COMPRESSION Opus, MP3, Vorbis, Musepack, AAC, ATRAC, Windows Media Audio Lossy (WMA lossy) Lossless Formats WAV and AIFF 1991 - MS and IBM - WAV = Waveform Audio File Format -.wav,.wave 1988 - Apple - AIFF = Audio Interchange File Format -.aiff,.aif both originally lossless and uncompressed formats for LPCM supported everywhere, WAV can be on the web WAV is limited by 4 GB filesize - 6.8 h sound Extension BWF is used in radio journalism - timecode, metadata, up to 16 EB -.bwf or.wav 1-4 300 000 000 Hz, up to 65 535 channels - used even for non- audio signal Sound 11  AIFF-C compressed, WAV can be also compressed FLAC = Free Lossless Audio Codec, royalty-free open audio coding format -.flac 2001 - Josh Coalson - now under Xiph.Org Foundation, GPL and BSD licence supports LPCM 4 - 32-bit, up to 655 350Hz, up to 8 channels reduces size to 50-70 % can be streamed - TIDAL, supports taggs, ReplayGain online music selling - Bandcamp uses RLE (like JPEG) supported everywhere, can be used in HTML5 Monkey’s Audio, ALAC 2000 - Monkey’s Audio - Matthew T.Ashland -.ape freeware, better compression than FLAXC, requires more CPU power, mulithreaded supported on Pc, not so much on Apple products 2004 - APple Lossless Audo Codec - Apple Inc. -.m4a or.caf originally proprietary, now Apache 2.0 licence since up to 384 kHz 32-bit DRM, supported on iAll Lossy Formats exploits imperfections of human hearing eliminates sound we cannot hear or we are not sensitive to psychoacoustic models Sound 12  used in radio broadcast, streaming video, telephony… MP3 = MPEG-1 Audio Layer III or MPEG-2 Audio Layer III, ISO/IEC 11172-3 and ISO/IEC 13818-3 1993 - Moving Picture Experts Group -.mp3 phenomenon but also damnation of quality audio - lossy majority of patents expired - open format up to 48kHz, 8-320bit/s, ID3 tags some streaming services best encoder: LAME = LAME Ain't an MP3 Encoder - LGPL licence Napster - P2P service for mp3 sharing, copyright was not really an issue 00's: boom of mp3 players, mp3 Discmans successor mp3PRO epicly imploded MP3 player 1998 - SaeHan Information Systems - MPMan up to 128MB with Smart Media card concept of online music distribution created in 1979 by Briton Kane Kramer Apple established Kramer as the inventor just because of lawsuit different company AAC, HE-AAC = Advanced Audio Coding, ISO/IEC 13818-7 1997 - AT&T, Dolby, Franhofer, Sony, Nokia - proprietary up to 96 kHz, 48.16 surround successor of MP3 HE-AAC = High Efficiancy AAC - ISO/IEC 14496-3 Sound 13  mostly for low bitrate, DAB+ & DRM radio mostly in H.264 and H.265 video, wide support Vorbis 2002 - Xiph.Org Foundation - open, BSD licence -.ogg competition of MP3, AAC, WMA, usually better 8-192 kHz, 45-500 kbit/s, 255 channels standard available to everybody wide support except Apple OPUS 2012 - Xiph.Org Foundation - open, BSD licence -.opus standard RFC 6716 successor Vorbis, most efficient audio codec today wide range of use cases, from telephony up to music 5-48 kHz, 6-510 kbit/s, 255 channels wide support used by YouTube, Signal, TeamSpeak, Discord, Wire, (DRM radio) Sound 14  LOSSLESS - MPL, RealAudio, ATRAC, WavPack, WMA LOSSY - AMR, AMR-WB, WMA, ATRAC, MP1, MP2, aptX, RealAudio, Speex, Lyra DOLBY 1982 - Dolby Laboratories - analog Dolby Surround - stereo and 1 surround channel 1987 - Pro Logic - added center channel 1991 - Digital - digital surround sound, AC-3 -.ac3 since 2017 free to use 5.1 = stereo + center + 2 surround + subwoofer (LFE), up to 48 kHz, 24-bit, 640 kbps 1992 - Batman Returns - optical track on film Sound 15  Plus - E-AC-3 - 6.144 Mbps, 13.1, better compression, backwards compatible with DD -.eac3 all uses lossy compression OTHER DIGITAL DOLBY TrueHD - 16 channels, 24-bit, 192 kHy, 18.64 Mbps Atmos - marketing term, uses objects and channels used in both soundbars and cinemas can be delivered in E-AC-3 or AC-4 2015 - AC-4 - up to 7.1.4, objects, part of DVB-T2 -.ac4 50 % - better compression than E-AC-3 - 192 kbps is enough for 5.1 DTS competitor of Dolby used by Spielberg in Jurassic park Digital Surround - similar to Dolby Digital DTS-HD Master Audio - similar to Dolby TrueHD, but up to 24.5 Mbit/s DTS:X - similar to Dolby Atmos, but less demanding speaker- wise, up to 11.2 Other Auro 3D - 9.1, 10.1 and 13.1 - speaker right above the head - Voice of GOD THX not a surround sound, but certification of sound quality made by George Lucas SDDS = Sony Dynamic Digital Sound - in older cinemas many many many other systems from Dolby, DTS and others almost always incompatible, needs different # of speakers Connectors and Connections Sound 16  Three-Pin XLR Connector IEC 61076-2-103:2004 and EIA RS-297-A Invented in 1950's Sometimes called Cannon after the inventor James H. Cannon Used for balanced audio signals - 2 wires + ground Single cable for each channel Microphones and speakers Locking mechanism, male and female connectors Phone Connector - Audio Jack Originally used in telephone switchboards - since end of 19th century several sizes - 2.5 mm, 3.5 mm, 6.35 mm mono, stereo - TRS, with microphone - TRRS TRRRS - ITU-T P.382, backwards compatible 5th pole used for active noise cancelling or binaural recording (second microphone) or power delivery Sound 17  Used for headphones, electric guitar output, speakers when used for balanced audio, stereo connector becomes mono RCA Connector invented by Radio Corporation of America in 1930´ Red and white - right and left/mono channels also used for analog - yellow and RGB only unbalanced or digital S/PDIF TOSLINK Toshiba Link - 1983 - JEITA RC-5720C Optical connection - no RF interference, grounding issues Red light with a wavelength of λ650 nm Usually black Mini-TOSLINK - fits in audio jack plug Used for S/PDIF S/PDIF Sony/Philips Digital Interface type of digital audio interface used in consumer audio equipment to output audio over relatively short distances uses orange RCA or TOSLINK Sound 18  Stereo PCM with 20 or 24 bit-depth, up to 48 kHz 7.1 in Dolby Digital or DTS AES3 "Professional" S/PDIF - IEC 60958 a standard for the exchange of digital audio signals between professional audio devices Used in broadcasting Stereo, 24-bit, 48 kHz With timecode Over XLR, BNC or IP network Dante 2006 - made by Audinate Uncompressed, multi-channel, low-latency audio over IP network Uses Ethernet for transmission - 100 MbE and 1 GbE Used in broadcasting, live events Proprietary 192 kHz, 32-bit AM and FM Radio AM = amplitude modulation, FM = frequency modulation, i.e. not a wavelengh AM are usually long-, medium- or short-waves - mainly because of reliability and ease of signal distribution in CZ long-wave - 270 kHz - Radiožurnál FM - on VHF - 87.5-108 MHz in EU since 50's, unlike AM enables stereo signal everywhere but Czech highways Sound 19  DAB/DAB+ = Digital audio broadcasting developed since 80's in EU, 1995 - 1st broadcast in Norway III-band - , L-band newer DAB+ now used almost everywhere instead MP2 uses HE-AAC v2 - more efficient compression bitrate approx. 128 kbps in CZ: ČRo, Impuls, Frekvence 1, Evropa 2…, approx. 62 % population coverage EPG, traffic info, SlideShow in PNG, HTML, but also video Podcasts and RSS = regularly released programme on Internet, streamed or downloaded by listeners begining of 00's - Adam Curry and Dave Winer either audio or also video on-demand uses RSS Feeds Rich Site Summary RSS written in XML - enables following of news websites, blogs, podcasts used by many DJs, Linux podcasts, popular science shows, ČRo, Respekt, Reportér Streaming Sound 20  since 90's, but very very limited by CPU power and Internet throughput internet/regular radio stations and on-demand content data are downloaded in small chunks, which are almost immediately played buffer - used to temporary store data for better stability necessary for live programmes, nice-to-have for non-live content now on mobile 5G, Starlink, satelite, fiber the problem is the capacity of content providers challenges in third world countries Sound 21