Category Archives: ACOUSTICS

REVERB – mÃ¥ste veta…

Analoga reverb Spring Reverb Uppfanns av nÃ¥gra ljudtekniker som skulle skapa en ljudeffekt som lät som Ã¥ska till radion med hjälp av att skaka spiralfjädern frÃ¥n en grammofon pickup. De upptäckte att ljud som passerade denna fick ett typ av reverb och sÃ¥ uppstod spring reverbet. Plate Reverb Är en fyrkantig metallplatta inuti en ljudisolerad box. Metallplattan kan vara upptill en meter i kvadrat. Signalen bussas ut frÃ¥n aux in i boxens cylinder som omvandlar den till ljudvÃ¥gor som sedan pÃ¥verkas av metallplattan. Förs vidare ut till en pramp och tillbaka…

Acoustics of Small recording studios

Under cubstruction….. At first we have to think about the ambience of the room. Recording studios should of course be quiet. The distance from where we are recording is also very important, because of the behaviour of the sound in enclosed spaces. Reflections, reverberation time etc. The distance controls the amount of direct and indirect sound from the source. The response of low frequencies is smoother in larger rooms and more difficult to control in smaller recording studios and listening rooms/control rooms. There are favorable room dimension ratios that are…

Modal Resonances

What is modal resonances? This is the resonance phenomena that you will find in any enclosed space. The dimensions of the area, the frequency of the sound, the reflection surfaces, they are all parameters that change how sound behaves in these areas. You can read a great explanation in this great book that we read in the Electroteqnique B course in Mittuniversitetet, (where I attend) the book is  “Master handbook of acoustics 5 edition” about Modal resonances; “Modal resonances are preferred frequencies where energy is concentrated. Most musical instruments use…

Reflection, diffraction, refraction

Reflection of sound is a phenomena that emerges when sound hits something. Its the reflections in a room that tells us about the shape and size of a room and help us define the charactaristics of it. Specular reflections means that sound behaves like rays of light; the angle of incidence is equal to the angle of reflection. This is described by Snells law. Flutter echoe is a type of echoe that emerges when we have two paralell walls is placed in a certain distance to each other. The sound…

Diffusion

Diffusion is a measurment of the spread of sound energy in a specific space. Why do we need diffusors? We need it because we want to obtain equal intensity in every frequency-area or “frequency -band”. You can measure diffusion in a room by measure the decay in different spots in the room. Good diffusion leaves a graphic of a exponential type, a straight line. And you can also measure the reverberation time in different spots where good diffusion leaves the same reverberation time in these spots.  

Comb filter effect

Comb filter effect is the effect that is created for example when two exact same sound signals are added and one of them is just a bit delayed. Signal a and b. Signal b hits the down-phase of signal a:s waveform with an equal “up-phase” and “turns off” frequencies which creates this effect. This effect is mostly auidible in higher frequencies. For example, when you listen to a mono-recording through stereo speakers, this effect will emerge as soon as you are moving from side to side and not sitting right in…

Reverberation

How does sound behave in a room? And what is really reverberation? When sound is generated within a space, a room, a hall, a church; the sound grows to a certain level. This level is called the equilibrium point. The more sound energy, the higher equilibrium. When the sound is turned off, it takes a certain time for the sound energy to decay to the point that you will not hear it. This is reverberation.  Reverberation is as you all know a very important parameter for creating good quality sound.  It is…

Sound Absorbtion

There are generally three types of sound absorbers; Volume or resonance absorbers. Most effective at lower frequencys. http://www.audioholics.com/room-acoustics/helmholtz-resonant-absorber   ”Helmholtz resonance” is the phenomenon of air resonance in a cavity. The name comes from Hermann von Helmholtz who was the author of the classic study of acoustic science. 2.    Panel absorbers Most effective at lower frequencys. http://dogbreath.de/misc/PlaneAbsorberResonance.pdf ”Base-traps” 3.   porous absorbers Most effective at higher frequencys.   The energy of sound can not be destroyed, but it can change from one form to another The vibratory energy of sound…