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series of presentations that focus on sound and audio, as well as its systems
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Sound Pressure Waves Sound wave defines as “are vibra1ons traveling through the air and pertain to receive by the ear.” When an object is struck, plucked, blown, it compresses and expands the air around it, producing the sound. It has some characteris1cs called Frequency, Amplitude and Pitch.
Frequency – expressed in Hz, is the number of cycles that a vibra1on completes in one second. Amplitude– expressed in dB, refers to a loudness and soDness of a sound. Pitch– refers to the highness or lowness of a Sound.
PHYSICS OF SOUND
Sound Pressure Waves
Waveform Characteristics
Amplitude
Frequency
Pitch
Octaves
Wavelength
Reflec1on of Sound Diffrac1on of Sound
Loudness Levels: The dB Sound Pressure Level
It also have 2 types called Longitudinal
and Transverse waves. They have the
regions known as Compressions and
Rarefac5ons. The compressions are
regions of high air pressure while
the rarefac1ons are regions of low
air pressure.
Longitudinal
Transverse
Reflec>on of Sound
Sound reflects off a surface at an angle
equal to its ini1al angle of incidence
This basic property is the cornerstone of
the complex study of acous1cs.
Behaviour of sound waves
Diffrac>on of Sound
Sound has the ability to bend
around an object in a manner that
r e c o n s t r u c t s t h e o r i g i n a l
waveform in both frequency and
amplitude
(rela1ve to the obstruc1ng
obstacle).
Frequency and Pitch Every Vibra1on has a frequency, and generally humans with golden ears can hear from 20Hz – 20,000Hz. Frequencies below the low end are called infrasonic and at the high end are ultrasonic. They are felt or sensed more than heard. Pitch refers to the rela1ve tonal lowness or highness of sound. The more 1mes per second a sound source vibrates, the higher the pitch.
Octaves
An octave is the interval between any two frequencies that have a ra1o of 2:1. Octaves are grouped into bass, midrange and treble. Star1ng 20Hz, the first octave is 20Hz to 40Hz, second is 40 Hz to 80Hz, third is 160Hz, and so on.
Wavelength
The actual distance in the air between the beginning and the end of a cycle.
Low Bass first and second octaves (20 Hz-‐ 80Hz) -‐ Power, Boom and Fullness. Upper Bass third and fourth octaves (80Hz-‐320Hz) -‐ Midrange 5th, 6th, and 7th octaves (320Hz-‐2,560Hz) -‐ Gives sound intensity Upper Midrange 8th octave (2,560Hz-‐5,120Hz) -‐ Our ears are most sensi1ve. Treble 9th and 10th octaves (5,120Hz-‐ 20,000Hz) -‐ Gives sound quality of brilliance and sparkle.
Low Bass Upper Bass Midrange Up Mid Treble
1 Cycle
Loudness Level
The system used to measure sound pressure level (SPL) is decibel (dB).
Sound Pressure Level -‐ Is the pressure of sound vibra1on measured at a point. -‐ Usually measured with a sound pressure meter.
The Decibel (dB)
The decibel (dB) is used to measure sound level, but it is also widely used i n e l e c t r o n i c s , s i g n a l s a n d communica1on.
The Ear and The Psychoacous0cs of Sound
The Ear
The Outer Ear
Pinna -‐ Aids localiza4on especially at higher frequencies. Ear Canal -‐ Not straight, cross sec4on is oval
The Middle Ear
-‐ Mechanical Amplifier between Air and inner air fluid. Ear Drum (Tympanic Membrane) -‐ Covered by Mucus Membrane and the first loca4on for transduc4on of sound. Ossicles (Middle Ear Bones) -‐ 3 smallest bones -‐ Hammer -‐ Anvil -‐ S4rrup -‐They serve to transmit sounds from the air to the fluid-‐filled labyrinth (cochlea). The absence of the auditory ossicles would cons4tute a moderate-‐to-‐severe hearing loss. The term "ossicle" literally means "4ny bone“. Eustachian Tube -‐ In adult humans the Eustachian tube is approximately 35 mm (1.4 in) long. It is named aSer the sixteenth-‐century anatomist Bartolomeo Eustachi. -‐ -‐ is a tube that links the nasopharynx
The Inner Ear -‐ is mainly responsible for sound detec4on and balance. Ves0bular system -‐ Balance and monitors all 3 dimensions. Cochlea -‐ dedicated to hearing; conver4ng sound pressure paVerns from the outer ear into electrochemical impulses which are passed on to the brain via the auditory nerve. -‐cone shaped spiral
The Cochlea -‐the cochlea is best understood when “unraveled” -‐Footplate of the s4rrup aVaches to the window -‐round window acts as a Pressure Relief Mechanism
Wave Mo4on in the Cochlea
-‐ Analogous to ocean waves approaching a beach -‐ Low frequency waves crest close to the “shore” (apex)
-‐ High frequency crest far from “shore”(near base)
Auditory Nerve -‐ a collec4on of 25,000 fibers from each hair cell to brain stem -‐ Certain fibers carry certain pitch info -‐ It is less than the diameter of a spaghe_ noodle
Perceived Sound vs Measured Sound Amplitude and loudness are related in one main way. Amplitude is the magnifica4on of vibra4ons that cause sound. The greater the magnifica4on of vibra4on that caught the sound, the higher the volume and loudness.
What is a Bad Sound???
-‐Noise is any unwanted sound -‐Very subjec4ve
-‐What is the preferred sound of a: -‐ Door Closure? -‐ Electric Guitar? -‐ Piano/ keyboard
Hearing Loss -‐is a par4al or total inability to hear. -‐ It is caused by many factors, including: gene4cs, aging, exposure to noise, illness, chemicals and physical trauma.
Conclusion -‐Our ears are the most expensive (priceless) piece of sound analysis equipment.
Acous&cs -‐is the science of sound and factors affec&ng our hearing. This field is divided into various subfields.
-‐ Physical -‐Bioacous&cs -‐ Architecture -‐ Musical -‐ Psychological -‐ Physiological
Physical Acous&cs -‐studies airborne, audible sound, infrasound (below audible frequencies), and ultrasound (above audible freq.). It examines propaga&on and absorp&on of all sound frequencies in air, and other gases, liquids , semisolids, and solids.
Musical Acous&cs -‐ Considers the workings of physical and electronic musical instruments. Rela&ve to their construc&on, materials and shape such as:
-‐ Violins -‐ Guitars -‐ Pianos -‐ Trumpets -‐ Drums -‐ Etc.
Psychological Acous&cs -‐ Studies the brain’s signal processing func&on. Which is necessary for sound to be Heard or interpreted.
Physiological Acous&cs -‐ Ear study in an important detector and modifier of audible sounds and its opera&on.
Bioacous&cs
-‐ Studies all aspects of acous&c behavior in animals.
Architectural Acous&cs -‐ Aims to maximize the clarity of music or intelligibility of speech in enclosed spaces, like in concert or lecture halls. -‐ It deals with the structures of the room boundaries, in terms of sound isola&on, sound absorp&on, reflec&ons and diffusion.
Wallace Clement Sabine
An American physicist who founded the field of architectural acous&cs.
Reverbera&on Time (RT60) Is generally defined as the &me required for the sound pressure level in an enclosed space to decreased 60-‐dB.
W. C. Sabine’s RT Equa&on RT60 =0.049 V/Sa V=Volume of room in [3 S=surface of the area in [2
a=average absorp&on coefficient
Example: V=445500 cu.[. (30’ x 90’ x 165’) S=45000sq.[. a= 0.35 RT = 0.049 x 445500 =1.39sec. 45000 x 0.35
A sound wave can be controlled in one of three different ways
The Control Room
Some common misconcep&ons about acous&c materials
-‐ That the proper&es of acous&c materials are the same
except for their appearance.
-‐ That acous&c materials just absorb sound.
-‐ That by using absop&ve acous&c material as a wall will prevent sound to pass thru.
Basic Proper&es of acous&c materials -‐some materials absorb soundwaves while other materials reflect soundwaves. -‐not all absorp&ve material absorb all sound frequencies equally. -‐not all reflec&ve materials reflect all sound frequencies equally.
Sound Absorp&on Coefficient
-‐defined as the percentage of absorp&on of sound energy impinging (to collide or strike ) upon a measured area of a material.
-‐W.C. Sabine defined a one square foot of an open window as having
an absorp&on coefficient of 1.
-‐usually stated for six standard sound frequencies of 125Hz, 250Hz, 500Hz, 1kHz, 2kHz and 4kHz.
Sound Transmission Class -‐is the simplified ra&ng of a barrier material of its capacity to prevent noise from penetra&ng to the other side of the material.
Sound Transmission Loss -‐the basic acous&cal property of a sound-‐isola&ng wall or floor / ceiling system. -‐it is the ability of the wall or floor/ ceiling system to resist being set into vibra&on by the impinging sound waves.
The Decibel (dB) The decibel (dB) is used to measure sound level, but it is also widely used in electronics, signals and communica&on. Decibel is a logarithmic ra&o of two quan&&es. The equa&ons for decibels are: -‐ For voltage, current, SPL, Distance: For Power: 20 log ( P1 / P2 ) 20 log ( X1 / X2 )
Audio Frequency Spectrum
The Audio Frequency Spectrum is the Bandwidth of the audible sound frequencies star&ng from the lowest frequency of 20Hz to the highest audible sound frequency of 20,000Hz Among musical instruments, the organ can produce the widest range from 20Hz to about 10kHz.
Audio Frequency Spectrum
Amplifier: How does it work?
-‐the output is a replica of the input waveform or sample signal.
-‐the signal does not travel from the input to the output.
-‐it is recreated from the power supply.
Loudspeaker
Loudspeaker , in short, converts electrical signals into audible signals. The s e l e cBon and i n s t a l l aBon o f a loudspeaker, and its design, should be guided by the need of coupling an electrical signal source to an acousBc place.
How a loudspeaker works? -‐signal current flows through voice coil, sets up magneBc field around the coil. -‐the magne/c flux of the magnet assembly interacts with the magneBc flux of the voice coil with force causes the coil to move in response to the signal current. • magne/c flux-‐ is a measure of the amount of magneBc field passing through a given surface (such as a conducBng coil).
Loudspeaker enclosures
We need to enclose the loudspeakers to prevent the rear wave from cancelling
the front wave parBcularly and the Low frequency region.
The Horn consists of a compression driver which produces sound waves with a small metal diaphragm vibrated by an electromagnet, aIached to a horn, a flaring duct to conduct the sound waves to the open air.
How a horn loudspeaker works. (A)compression driver (B) horn
Usefulness of Horns -‐More efficient than direct radiators. -‐BeIer control of direcBonal paIern of the output sound, parBcularly in the mids and highs.
3 Parts Tweeter – high frequency Squaker – middle frequency Woofer – low frequency
Loudspeaker DistorBons
-‐Harmonic distor/ons due to mulBple resonance of cones, and enclosures.
-‐when the low frequency distort in any manner,
it distorts the high frequency by flaIering off the peaks.
Overdriving and inter-‐ modulaBons
-‐overdriving the voice coil can cause it to leave the magneBc gap.
-‐inter-‐modulaBon appears as fullness of the higher frequencies and causes listener faBgue.
The Microphone Demys0fied
-‐ A transducer that transforms acous0cal energy into electrical energy. -‐ ”Energy” that i s be ing converted by the microphone is the sound pressure level (SPL), which is received by a diaphragm of the mic and is t h e n t r a n s f o rmed i n t o cor respond ing sma l l AC voltages.
Shure 55sh
Most common types of microphones
Dynamic -‐ It has a magnet that which can move within the coil of wire.
-‐ Uses electromagne0c induc0on.
-‐ does not need phantom power.
-‐ When sound hits the microphone capsule, it causes magnet to move within the coil and induces an electric current and flows along the audio cables to a mixer or amplifier. -‐can handle high SPL.
Dynamic Microphone
Ribbon Microphone -‐ a unique type of dynamic microphone that is based around a thin, corrugated strip of metal (oOen aluminum) or film suspended between two magne0c poles. -‐ this level is very low compared to typical dynamic mics, and a step-‐up transformer boosts both the output voltage and impedance.
-‐ Ribbon mics are very sensi0ve, but they are oOen quite fragile.
Carbon Microphone -‐ It consists of two metal plates separated by granules of carbon.
Condenser Microphone -‐require power from a baQery or external source. -‐The resul0ng audio signal is stronger signal than that from a dynamic. -‐Condensers also tend to be more sensi0ve and responsive than dynamics. -‐They are not ideal for high-‐volume work, as their sensi0vity makes them prone to distort.
Condenser Microphone
Phantom Power (48+)
Is a method for transmiVng DC electric Power through Microphone cablesto operate microphones that contain
Electric circuitry.
Microphone pickup paQerns
Microphone pickup paQerns
Mic Posi0oning for Vocals
Drum mics Posi0oning
Mic posi0oning for Acous0c Guitar
Mic Posi0oning For Piano
Mic Posi0oning for News Anchoring
Other Mic Posi0oning
Violin Trombone
Saxophone Flute
Mic Posi0oning for Orchestra
Stereo Mic Posi0oning
Stereo miking is the preferred way to record classical-‐music ensembles and soloists, such as a symphony performed in a concert hall or a string quartet piece played in a recital hall. Stereo mic techniques capture the sound of a musical group as a whole, using only two or three microphones.
Stereo Mic Posi0oning
End Of Discussion
The Audio Mixing Console
What is an Audio Mixer? -‐A resis3ve network designed to provide a means of combining several separate audio signal sources into one composite signal. -‐the network is designed so that changing the level of any one of the individual signal sources has no effect on the level or frequency characteris3cs of the other signal sources in the network.
Basic Func3ons -‐ Amplify Signals from Microphones, instruments and program sources of level required to drive power amplifiers to full power output.
-‐ Combine different signal sources.
-‐ Adjust each input (Gain, Level, Equaliza3on ).
-‐ Route each input to one or more designated outputs.
MIC / LINE
MIC / LINE
HEAD AMP GAIN
HEAD AMP GAIN
EQ
EQ
FADER
FADER
AUX OUT 1
AUX OUT 2
MAIN OUT LEFT
MAIN OUT RIGHT
AUX PRE
AUX PRE
AUX PRE
AUX PRE
Mixer Signal Flow
Audio cable / Snake cable
RCA and PL Jack Cable
Special Cables
Unbalanced vs Balanced
-‐lower noise due to “common mode rejec3on” (unwanted signal) -‐higher immunity to EMI -‐longer cable length -‐twis3ng of conductor causes electromagne3c field to be con3nually reversed with each full twist, prevents crosstalk with other cables.
-‐limited to a maximum of approximately 5-‐6 meters cable length. -‐no cancella3on of electro-‐ magne3c interference. -‐relies only on the shield strength to reduce noise. -‐crosstalk between two adjacent lines.
Equalizer -‐used in recording studios, broadcast studios, and live sound reinforcement to correct the r e s p o n s e o f m i c r o p h o n e s , i n s t r u m e n t p i c k -‐ups, loudspeakers, and hall acous3cs. -‐The most common equalizers in music produc3on are parametric, semi-‐parametric, graphic
Sound Processors -‐Passive devices alter sound directly. These are the form of: bass traps, diffusers, large halls, etc. -‐Ac,ve devices alter sound electronically. They may be electroacous=c devices like Compressors and digital delays either analog or digital.
Why do we need? -‐to remove the “ring” or feedback of sound systems, cleanup the muddy mix, compress signals, reproduce sound accurately, etc. -‐to enhance or highlight a musical part. -‐ To make a sound output more brilliant.
Filters audio filter is designed to amplify, pass or aIenuate (nega=ve amplifica=on) some frequency ranges.
Electronic Reverb or Delay Devices refers to the way sound waves reflect off various surfaces before reaching the listener's ear. From the first reflec=on to subsequent dense reverbera=ons in any given “volumetric parameter”.
Prac=cal Applica=ons of Reverb Devices
-‐Used as an effect to add texture to a dry signal .
-‐Used as an effect to determine the origin of the sound.
-‐Used as visualiza=on or ar=s=c expression of a certain sound.
Compressors and Limiters
These are voltage gain amplifiers that decrease signal upon a given level. They are best used as in –line devices to reduce the dynamic range of a signal.
Basic Controls Threshold. When this level is exceeded, the processor starts compressing (i.e., aIenua=ng, reducing volume). Ra,o -‐ determines how much the signal is “squezed” once the threshold is reached. a ra=o of 4:1 means that if input level is 4 dB over the threshold, the output signal level will be 1 dB over the threshold.
Basic Controls A3ack-‐ controls how fast the compressor reacts to the signal. Release-‐ how quickly it returns the signal to normal. Gain-‐ this control is oZen referred to as "makeup gain", as it makes up for t h e c omp r e s s i o n -‐ i n du c ed aIenua=on.
