Car Audio

I have been covering all the interior surfaces of our company car with our foam technology. I have our 2″ foam on the dash board and our 1/2″ foam on the windshield itself. I have our 1/2″ foam positioned between the speaker and the glass to minimize that first reflection point. The problem is keeping the tape stuck to the window when the outside air temperature is 120 degrees in the Sonora desert. There is 1/2″ on the ceiling and the rear windows. My goal is to over absorb this glass “fishbowl” and then peel back certain surfaces and hear what happens to the total sonic picture as far as absorption is concerned. Who knows if over absorption is even possible in a “fishbowl” let alone good sounding car audio.

The car audio sound system is made by bounce energy everywhere Bose and it does fill the “bowl” with sound energy from front and rear speakers. There are adjustments for bass, treble, and even mid range. One can use the fader control and change the energy distribution pattern between front and rear speaker systems. There is also a left/right balance control.

The auto or truck is at best your worst acoustical nightmare. What kind of room is this? Glass windshield front wall. Not only is the windshield made of glass, it is shaped in a convex manner to reduce air flow resistance on the outside of the vehicle and direct all the glass reflections back at the driver and front seat passenger on the inside. Yikes! Our side walls are also made of glass right at the ear level which is that critical listening plane. Rear walls are glass and if you push the right button on the console, the ceiling turns into glass also. Yeah ! more glass.

Stay tuned for sound checks.

www.acousticfields.com

What Are We Looking For In Hi – Fi ?

There is a school of thought in hi – fi that subscribes to the ideal that music played through our two channel system is supposed to sound as close to a live performance as possible. We are supposed to be acoustically positioned in the front row, live, with the artists in front of us. Two channel sound, I mean good two channel sound is supposed to recreate the original source performing live. I believe we are asking too much from our two channels and the room we are listening to it in.

There is no way to recreate the sound of a live event held in a large concert hall with current two channel playback equipment. There is no way even with home theater playback equipment. No software or digital program can recreate the sonic ambience of a live venue or the specific sonic nuances a large volume building can do for a 55′ low frequency wave. No rear channel speaker has ever convinced me that it has all the voices of the 60,000 member audience coming from its 6″ driver. None of these big room effects can be recreated in rooms with much smaller volumes. It is just not possible since the current laws of physics do not allow for it.

What we can do is emotionally connect to our playback systems. We do this by setting up our system in the best spot in our room. This will take awhile. We next find that right listening chair: the one that has a high enough back that we can support our heads without blocking the backside of our ears. Place diffusion/absorption on the front wall, rear wall, and ceiling. Middle and high frequency absorption on the side walls. Low frequency absorption throughout the 4 vertical walls; extra behind speakers.

Sit back. Listen at same level for 1 song. Increase level. Listen for 1 song. Increase level. Listen for one song. Did you find your emotion. It is there. Dancing is permitted.

www.acousticfields.com

Trade Show Sound

I have been attending audio trade shows over the last 6 months and have sat and listened in all shapes and sizes of rooms. The rooms are hotel rooms that have had ( in some cases) the bedroom furniture removed, so a manufacturer can set up their product and hopefully get some type of quality sonic presentation for customers to hear. My purpose was to try and understand what amplifier and speaker manufacturers are up against acoustically in these hotel rooms.

Moving across the frequency spectrum from low to high, first, we have the low frequency issues faced in all small room environments. They are very present in these small hotel rooms and even have glass windows that rattle from sound pressure. Bass bleed from neighboring rooms must be dealt with through diplomacy. Middle and high frequency reflections from odd shaped rooms causes numerous issues at the listening position. Exhibitors try and set up their systems the best way possible, but it is difficult when the room is L – shaped. Parallel and rectangular room boundaries provide for better and more predictable lateral reflection control at the listening position.

Any product one designs and uses in the trade show rooms must be able to stand on its own two, three, or four feet. The hotel does not want holes placed in their room walls for installing room acoustic treatment. Holes in the carper are fine. Any acoustical treatment must be able to be free standing and not mark or damage the existing room walls.

I would like to remove some of the walls. It would sure make my task easier and I am certain some of the exhibitors would help me. Come to the Rocky Mountain High Fi show in October to see how I did. We are in the Usher room along with six other rooms.

www.acousticfields.com

Personal Listening Environment

Imagine a room where low, middle, and high frequency energy is dealt with in a systematic and effective way with all new room acoustic technology. This room would have all the necessary type and amount of low frequency absorbers placed at the proper positions in the room. Horizontal and vertical diffusion will create a two dimensional sound field for the middle and high frequencies on all front, rear, and ceiling surfaces.

The room would have new foam technology to absorb just the right amount of middle and high frequency energy to reduce reflections from the room walls at the listening position. Imagine a room where the ceiling is a blend of diffusion and absorption to give our sound stage presentation height beyond the ceiling boundary.

Our sound stage in our room will have a height, width, and depth that extends beyond the existing room boundaries. Instruments and vocals will have distance and distinct separation between them. There will be air in our sound stage and the visceral connection to the music will be immediate and without effort. You will be taken out of the first row and put on stage with an instrument to play. You will have no choice but to play it. Imagine this room fits inside your existing room with no screws, nails, or sawdust from power tools.

Watch for our PERSONAL LISTENING ENVIRONMENT (PLE) this Christmas.

WWW.ACOUSTICFIELDS.COM

Noise

The term noise is defined in many ways. The first definition I found of noise in all the electronic dictionaries I surveyed was about our industry of music. Merriam-Webster summed up most publications efforts by stating that noise is “sound; especially one that lacks agreeable musical quality or is noticeably unpleasant”. This is interesting. We have an individual’s opinion as the basis for the definition itself.

Sound that “lacks agreeable musical quality” can be sound that my grandmother would call noise, but I would call Santana. I do not think I would call any of her music noise, but I would surely call the recording process that was used noisy. I do not think I would call younger people’s music as noise. I would call it noise, however, if the compressed mp3 music they are listening to is leaking out from around their ear plugs and entering my ears at the DMV. I am certain the 3 sets of bones in their middle ears are calling all that pressure noise. If not now, they will be in say, 10-20 years.

“Agreeable music quality” must be replaced with “disagreeable music quantity” It really is the sound pressure and level of the pressure that causes our brains to label the phenomenon “noise”. Different pressure levels produce different reactions in different people. It probably is a defense mechanism to protect our hearing.

People tell me if you really want to “hear” pressure go stand next to a jet taking off. Maybe so, I have never done that. I have stood at the starting line where two, nitro burning, 8,000 horse power, funny cars were staged and ready for a green light. When the light hit green, I recorded 170 db, my pant legs were flapping so hard they made noise and my lips were bent out of shape as if my head was out a car window at 120 mph. Now thats noise.

www.acousticfields.com

Audio Speakers

We can make some interesting and not really discussed observations about our audio speakers. Lets keep our discussion in the playback domain of our recorded source material. Our playback system will need to be set up in a room with 4 walls, ceiling, and floor.

Our audio speakers will be a two channel system operating in stereo mode. Our first observation must deal with the reflections which occur from the sound generated by our audio speakers and the walls, floors, and ceilings. Primary, secondary, and tertiary reflections all confuse the direct energy which is the energy that reaches our ears in the shortest time frame. Sound that travels in a straight line from our audio speakers to our ears is called direct sound. Sound that is reflected off of room boundary surfaces is called reflected sound.

One of the sonic consequences of these reflections between our audio speakers and the room is a term called coherent interference. This is the name for the sound issues that result from all the room boundary reflections bombarding the listening position with all this “interference”. This coherent interference affects the lower mid and upper bass regions of our sound presentation. Vocals are smeared and blurred and instruments in this region may not be heard.

www.acousticfields.com

Recording Studios

Recording studios must deal with the acoustic of the room in order to make a living or generate income from their studio. Wall reflections and room modes must all be addressed in order for the engineer to hear the sounds produced from the musicians instead of the room sound. The engineer must separate the room sound from the mixed sound.

The primary, secondary, and tertiary side wall reflections in recording studios must be controlled in some acoustical manner in order to minimize their impact at the monitoring position. The engineer wants to hear the sound that comes directly out of his speakers and reaches his ears before the side wall reflections interfere with this wanted direct sound. Similar room boundary reflections must be controlled for the sides and rear channel recording.

In the recording studios I have seen, special care is given to placing the entire monitoring system in a place in the room that is free from room mode issues. Room modal issues occur between two parallel surfaces and their intensity varies with room volume. Room modes can hide or over emphasize certain frequencies. We want to hear everything at the mix position. We don’t want the room hiding or producing anything extra for us to have to deal with. Dealing with artistic, sensible, individuals can produce enough “sound” of their own let alone having to deal with the room mouthing off.

www.acousticfields.com

Sound Deadening

Sound deadening is an interesting blend of words people use in Goggle search engines. I guess this phrase sound deadening refers to a process of making sound “dead”. Lets explore how we would do this.

We all know from our introductory physics class that energy really can’t be destroyed. We all remember that energy can be transformed into another energy type but not destroyed. If we are going to have a sound deadening process introduced in our rooms, we must change the electromechanical sound that comes from our speakers and change it into some other energy form in order to minimize its sonic impact. Absorption of sound is a process where sound energy is converted to heat through the use of some type of sound absorbing material. Once sound energy is converted to heat through the absorption process, it is lost forever.

The sound absorption process can be accomplished with foams, fabric type materials, activated carbon, and numerous other material types that have the necessary physical characteristics to absorb sound energy. When we absorb sound energy we change its form to heat and all sound energy is reduced that goes through the sound absorbing device. Did we make our sound go dead? Our ears will think so if we use too much of any sound absorbing material type.

www.acousticfields.com

Foam Sound

Foam sound is a term that people use in search engines, especially Goggle. It is an odd choice and arrangement of words. It is a blend of science and culture. This misuse of terms happens a lot and one can find these interesting search words and phrases by using Goggle keywords and phrases search engine. It is fun sometimes to see how people perceive the science of acoustics and how they use the science nomenclature in unique ways and blend it with culture.

I try and figure out what someone is looking for when they use the search term ” foam sound”. They probably want some type of lightweight, economical, foam material to reduce unwanted room reflections. Maybe the room is too “loud” and they seek to lower the noise floor. I don’t know how they would ask for it at the store. Would they ask for foam sound or sound foam?

They may mean the type of sound that is created when sound strikes the foam. Sound energy does take on the “sound” of certain material types it strikes. If you strike glass with sound energy such as in our vehicles you get “glass sound”. When you strike wood, you get “wood sound” . Wood sound is much better than glass sound. You can test this by sitting and playing your car stereo system for a period of time. Don’t drive the car and perform this test. Stay static, so you don’t have tire, engine, and wind noise created. Stay still, it won’t take long and it definitely will hurt.

www.acousticfields.com

Sound Panels

The search term “sound panels” is another example of how people take things they are familar with and put them together to try and communicate something. Unfortunately, this process only confuses the issues.

I think people use the term sound panel or sound panels to mean a structure that reacts to sound in some way. My best guess is that sound panel means some sort of panel or structure that does something for or to sound. To an engineer, it means a panel that produces sound energy. I think to most people it means a panel that absorbs sound because their environments they are in are too noisy.

Sound panels could be a panel with speakers in it as is used in sound reinforcement venues such as concerts. A PA or public address system could be referred to as a sound panel. An electrostatic speaker could be a sound panel. An electrostatic speaker is a panel type structure that produces sound energy through a vibrating membrane constructed of screen wire which an electrical current is passed through.

Electrostatic speaker manufacturers would cringe at their technology and sound producing processes as using screen door wire. I know something of their pain when I hear the term sound panel.

www.acousticfields.com