Chris Degman
Modern Recording Techniques        
i. studio acoustics and design
•	When designing or redesigning an acoustic space, the following basic requirements should be considered:
1.	Acoustic Isolation: This prevents external noises from transmitting into the studio environment through the air, ground or building structure. It can also prvent feuds that can arise when excessive volume levels leak out into the surrounding neighborhood.
2.	Frequency balance: The frequency components of a room should't adversely affect the acoustic balance of instruments and/or speakers.  Simply stated, the acoustic environment shouldn't alter the sound quality of the original or recorded performance
3.	Acoustic separation: The acoustic environment should not interfere with intelligibility and should offer the highest possible degree of acoustic separation within the room ( often a requirement for ensuring that sounds from one instrument aren't unduly picked up by another instrument's microphone)
4.	Reverberation: The control of sonic reflections within a space is an important factor for maximizing the intelligibility of music and speech. No matter how short the early reflections and reverb times are, they will add an important psychoacoustic sense of space in the sense that they can give our brain subconscious cues as to a room's size, number of reflective boundaries, distance between the source and listener, and so forth.
5.	Cost factors: Not the least of all design and construction factors is cost. Multimillion-dollar facilities often employ studio designers and construction teams to create a plush decor that has been acoustically tuned to fit the needs of both the owners and their clients, Owners of project studios and budget-minded production facilities, however, can also take full advantage of the same basic acoustic priciples and construction techniques and apply them in cost-effective ways.
ii. Studio types
•	Some of the more common studio types include:
1.	Professsional music studios
2.	Audio-for-visual production environments
3.	Project studios
4.	Portable studios
A. The professional recording studio
•	The professional recording studio is first and foremost a comercial business so its design, decor, and acoustical construction requirements are often much more demanding than those of a privately owned project studio
B. The audio-for-visual production environment
•	An audio for visual production facility is used for video, film and game post-production(often simply called post) and inclused such facets as music recording for fim or other media (scoring), score mixdown, automatic dialog replacement (ADR, which is the replacement of on- and off screen dialog to visual media) and Foley ( the replacement and creation of on- and off-screen sound effects)
C. The project studio
•	The design and construction considerations for creating a privately owned project studio often differ from the design considerations for a professional music facility it two fundamental ways:
1.	Building constraints
2.	Cost
D. The portable studio
•	In this digital age, it goes without saying that the Mac, PC and other hardware options are available in portable configurations that can be easily take on the road. With their increased power, portablility and inherent cool factor, these small, lightweight powerhouses can often dish out serious mucic production power with the big boys. Of course, the real power and flexibility of a portable recording system rests in the freedom that it offers to escape the confines of the studio, for example would you like to:
1.	Record a guitar overdub in the local high school gym?
2.	Record your band's latest performance with a handheld recorder?
3.	Sample a car dor slam at a mexican market?
iii. Primary factors governing studio and control room acoustics
•	Regardless of which type of studio is being designed, built and used, a number of primary concerns shold be addressed in order to achieve the best possible acoustic results, such important and relevant aspects of acoustics include:
1.	Acoustic Isolation
2.	Symmetry in control room and monitoring design 
3.	Frequency balance
4.	Absorption
5.	Reflection
6.	Reverberation
A. Acoustic isolation
•	The reduction in the SPL of a sound source as it passes through an acoustic barrier of a certain physical mass is termed the transmission loss (TL) of a signal. This attenuation can be expressed (in dB) as:
TL = 14.5logM+23
Where TL is the transmission loss in decibels, and M is the surface density (or combined surface densities) of a barrier in pounds per square foot ( lb/ft2)
•	Because transmission loss is frequency dependant, the following equation can be used to calculate transmission loss at various frequencies with some degree of accuracy:
TL = 14.5logMf-16
Where f is the frequency in hertz
•	Walls
•	When building a studio wall or reinforcing an existing structure, the primary goal is to reduce leakage (increase transmission loss) through a wall as much as possivle over the audible frequency range. This is generally done by:
1.	Building a wall structure that is as massive as is practically possivle ( both in terms of cubic and square foot density)
2.	Eliminating open joints that can easily transmit sound through the barrier
3.	Dampening structures, so that they are well supported by reinforcement structures and are free of resonances.
Material			Thickness (inches)			Surface density(lb/ft2)
Brick                                                                        4                                                                              40.0
                                                                                   8                                                                              80.0
Concrete(light)                                                    4                                                                              33.0
                                                                                  12                                                                           100.0
Concrete(dense)                                                 4                                                                              50.0
                                                                                  12                                                                           150.0
Glass                                                                          -                                                                                3.8
                                                                                     -                                                                                7.5      
                                                                                     -                                                                              11.3
Gypsum wallboard                                              -                                                                                 2.1
                                                                                    -                                                                                 2.6
Lead                                                                      1/16                                                                              3.6
Particle board                                                        -                                                                                 1.7
Plywood                                                                   -                                                                                 2.3      
Sand                                                                           1                                                                                8.1
                                                                                     4                                                                              32.3   
Steel                                                                           -                                                                              10.0
Wood                                                                         1                                                                                2.4        
•	The following guidelines can be helpful in the construction of framed walls that have high transmission losses:
1.	If at all possible, the inner and outer wallboards should not be directly attached to the same wall studs. The best way to avoid this is to alternately stagger the studs along the floor and ceiling frame, so that the front/back facing wals aren't in physicalcontact with eahother
2.	Each wall facing should have  a different density to reduce the likelihood of increased transmission due to resonant frequencies that might be sympathetic to both sides. For example one wall might be constructed of two 5/8 inch gypsum wall boards, while the other wall might be composed of soft fiberboard that's surfaced with two 1/2 inch gypsum wallboards
3.	If you're going to attach gypsum wallboards to a single wall face, you can increase transmission loss by mounting the additional layers (not the first layer) with adhesive caulking rather than using screws or nails
4.	Spaceing the studs 24 inches on ceter instead of using the traditional 16 inch spacing yields a slight increase in transmission loss.     
5.	To reduce leakage that might make it through the cracks, apply a bead or nonhardening caulk sealant to the inner gypsum wallboard layer at the wall-to-floor and corner junctions
•	Optionallh, a specially designed cavity called a soffit, can be designed into the fron-facing wall of the control room to house the larger studio monitors
•	Typical wall constructions materials enclude:
1.	Concrete: This is the best and most solid material, but it is often expensive and it's not always possible to pur cement inot an existing design
2.	Bricks (hollow-form or solid-facing): This excellent material is often easier to place into an existing room than concrete
3.	Gypsum plasterboard: Building multiple layers of plasterboard onto a double walled stud frame is often the most cost and sesing efficient approach to reducing resonances and maximizing transmission loss. It is oftena good ideah to reduce these resonaces by filling the wall cavities with rock-wool or fiberglass, whole bracing internal structure to add n extra degree of stiffness.
•	Floors
•	Low-frequencyies can travel through floors easily, using a rubber underlay, or a u-boat floating floor can reduce vibrations from low frequency leakage.
•	Risers
•	The most comon floor leakage can be caused by the drums, so using a drum riser can reduce leakage.
•	Iso-rooms
•	Iso-rooms are acoustically isolated or sealed areas that are built into a music studio, these areas are used to separate louder instruments from softer ones and vice versa, in order to reduce leakage, and to separate instrument types by volume is to maintain control over the overall ensemble balance, for example:
1.	To eliminate leakage when recording scratch vocals, a vocalist might be placed in a small room while the rhythm ensemble is placed in the larger studio area.
2.	A piano or other instrument could be isolated from the larger area that is housing a full string ensemble
3.	A B3 organ could be blaring away in an iso-room while backing vocals are being laid down in the main room.
•	Noise isolation within the control room
•	Here are a few examples of the most common problems and their solutions:
1.	Replace fans with quieter ones. By doing some careful web searching or by talking to your favorite computer salesperson, it is often possible to install CPU and case fans that are quieter than most off the shelf models
2.	Regulate case fan speeds with variable pots. Gamers will often regulate their computer fans in order to keep noises down, Care needs to be taken to monitor the CPU/case temp so as not to harm your system
3.	Install hard drive enclosures to reduce internal hard drive noises. These enclosures are designed to acoustically encapsulate 3.5 inch hard drives into a design that fits into a 5.25 inch hard drive bay.
4.	Place the computer in an acoustically isolated alcove, again care needs to be taken to monitor the tempuratures.
5.	Connect studio computers via a highspeed network to remote server location, By connecting a silent computer to a central computer via highspeed network, not only is it possible to eliminate computer related noises but it is also a relatively simple matter to connect various production and business related terminals to a central server that can be backed up according to a scedule.
•	Frequency balance
•	It is important to maintain a flat frequency response in a room without it creating its own particular sound coloration.
•	Reflections
•	Opposing parallel walls give rise to a phenomenon known as standing waves, and these can occur when sound is reflected off of parallel surfaces and travels back on its own path, causing interferance with a rooms amplitude response.
•	flutter echo is a condition that occurs when parallel boundaries are spaced far enough apart that the listener is able to discern a number of discrete echoes.
•	Absorption
•	Whenever a sound strikes a material the amount of acoustic energy thats absorbed relative to the amount that reflected can be expressed as a simple ratio known as the materials absorption coefficient, represented by:
•	A = Ia/Ir Where I is the sound level in decibels that is absorbed by the surface, and Ir is the sound level that is reflected back from the surface.
•	High  frequency absorption
•	High frequency absorption is acomplished through the use of dense porous material such as fiberglass, dense fabric and carpeting
•	Low frequency absorption
•	Low frequencies are best damped by pliable material.
•	Bass traps are designed in a number of ways:
1.	Qyarter wavelength trap
2.	Pressure zone trap
3.	Functional trap
•	The quarter wavelength trap
•	The quarter wavelength bass trap is an enclosure that is one fourth the depth of the of the offending frequencies fundamental and is often built into the rear facing wall, ceiling, or floor structure and covered by metal grating to allow foot traffic
•	The pressure zone trap
•	The pressure zone bass trap absorber works on the pricipal that large boundaries are doubled int the area of 90o angles, by putting absorptive material at these boundaries the build-up pressure could be partially absorpted.
•	Functional trap
•	functional bass traps are generally material formed into tube or halft tube structures that is rigidly supported as to reduce structural vibrations
•	Room reflections and acoustic reverberation
•	As was stated in the latter part of chapter two, the reverberated signal can be broken down into three components:
1.	Direct sound
2.	Early reflection
3.	reverb