From the Desk of Art Noxon
Art Noxon is a fully accredited Acoustical Engineer with Master of Science degrees in Mechanical Engineering/Acoustics and Physics. A Professional Engineer since 1982, he is licensed in Oregon to practice engineering in the public domain with the specialty area of acoustics. A prolific inventor, he developed and patented the iconic TubeTrap, the original corner-loaded bass trap/treble diffuser, 150 other acoustic devices and counting. Lecturer, writer and teacher of acoustics, he has presented 7 AES papers, numerous magazine articles, white papers and blogs. He is president of Acoustic Sciences Corporation, the company he founded in 1984.
Studio performance...Yes, FFT analysis has gotten pretty inexpensive since those early days in the mid 1980’s when we had to buy the Crown Techron 12 or 20 for something well over $10k...but regardless of when or how much it cost, once you have the FFT analysis, then what? If the FFT waterfalls look smooth and fast, does that mean the studio sounds good? If the freq response measures pretty flat, does that mean your mix will hold together?
Studio performance...Yes, FFT analysis has gotten pretty inexpensive since those early days in the mid 1980’s when we had to buy the Crown Techron 12 or 20 for something well over $10k...but regardless of when or how much it cost, once you have the FFT analysis, then what?
If the FFT waterfalls look smooth and fast, does that mean the studio sounds good?
If the freq response measures pretty flat, does that mean your mix will hold together?
Question: I’m the organist at a church with a beautiful pipe organ in a historic stone church. I’m sure it sounded great in the old days they covered the floor with beautiful carpet years ago and lost the sanctuary lost its reverb. They won’t remove the carpet to get the reverb back….Do you know of any clear paint I can use to remove the carpet’s acoustics so I can get the reverb back into the sanctuary?
The formula f = 170/sqrt(m x d) is often quoted as applying to membrane bass traps. The m term is surface weight (lb/sqft) of the membrane and d is the depth of the air cavity behind the membrane. See Home Recording Studio, Gervais, Fig 9.10 (Panel Trap Formula).
Sometimes yes, but usually not, depending on the kind or version of the Audio Measurement being made. My primary experience with audio measurement is in the realm of room acoustics so this will be the context of my response to this question.
The sonic MTF is how the clarity of sound or intelligibility of speech is physically measured. A similar system exists for measuring the clarity of lenses in optics.
It appears as a 3-D plot with the Modulation Level (dB) on the vertical axis, the Modulated Tone (Hz) on a horizontal axis and the Modulation Rate (Hz) on the other horizontal axis. A typical data point would be a Modulation Level of 15 dB for a Modulated Tone of 250 Hz at a tone burst or Modulation Rate of 8 Hz.
Back in 2009 I received a philosophical question, something not too different from "How many angels can dance on the head of a pin?" It's about how many people could hear the voice of Jesus at one time. Below I show the actual question followed by Section 1 of my answer. Here I idealized the physical listening conditions so that I could establish the maximum possible number of listeners. In later sections, which I will soon publish, I work towards more practical answers.
Sub bass is the frequency range the subwoofer make, typically below 45 Hz. It’s pretty difficult to buy bass traps large enough to absorb the power being put out by subwoofers. A subwoofer might be rated at 1000 watts. One horsepower is about 750 watts, so a subwoofer is rated as a 1¼ horsepower air pump. What happens to all that power anyway?
One time I was asked to dial in a huge hifi demo room at a high end audio show in Newport, CA without using TubeTraps. The room was a large conference room, with a 12’ ceiling and the width and length were both in the 50 to 60’ range. It was a huge room and it would take a truck load of TubeTraps to try to get this room to play. It was running big Magico speakers, Spectral electronics and MIT cables and that package deserved to sound great.
When it comes to measurement or assessment tools in acoustics, we have a problem when the tools we have do not agree with subjective interpretations. In this case we need a shimmer meter to better study and understand concert hall acoustics and guitar pedal sound, because in both venues, the concept of shimmering sound is a valued commodity.
It happened to Bob Hodas once and it was so unusual that he mentioned it in a MIX article on room acoustics. Actually, what he ran into could easily have been a live example of a technique we use in the design and set up of listening room and control room acoustics.
Contrary to popular belief the big problem with bass in hifi is not lumpy bass, standing waves, room modes, hot spots and suckouts. The big problem is sound masking.
That’s right, sound masking is what happens when an unwanted sound overpowers our ability to hear and discern the fine details of a wanted sound.
Bruce Swedien had recorded and mixed Thriller in 1982 and by 1987 he was still the top recording engineer in the world.
During the time Thriller was being made, I was graduating from college, my second masters degree, this time in physics, prior degree was Mechanical engineering/acoustics. I couldn’t get a real job, had 3 wonderful kids and ended up working in the city sewer, stringing and pulling an inspection video camera through the pipes.
The timeless image of HiFi is a high flying Persian carpet sporting a listening chair and a pair of loudspeakers. Yes, it’s true. A good sound system set up on a Persian carpet can transport any audiophile into a wonderful adventure in some other place and time.