Hz vs Church

“Hz vs Church” aims to use Churches [or other big sized public buildings] as post loudspeakers in order to create, unfold and play live various sounds which appear in the “aural surface” by using and manipulating in real time, different kinds of frequencies. The frequencies and sounds have been created by using tone generators. This project builds on the phenomenon of resonance [Hermann von Helmholtz], when one of the core ideas, is to use the pure sounds in a way that Pierre Schaeffer described as objects sonores [musical objects]. This, enables the audience to re-decode, perceive and redefine music by listening profoundly to some elements that obviously appear in numerous audio outputs, but not individually and instantaneously like in “Hz vs Church”. Some of the sounds are amplified ultrasound and infrasound frequencies. I also use various kinds of noise such as white, pink, brown and blue noise.

The main part of the performance consists of frequencies from 40-12000 Hz. Triangle, sawtooth, square and sinewave tone generators have been used to create them. Most of the sounds will be played in the same volume level, and this is because I would like to enforce the room to show up its own voice. One of my goals is to outline the diversity between the sounds. As the layers of its frequency are getting denser, a drone with various overtones is making reflecting sounds into the building. There are three types of reflections that people hear in a church or in an auditorium. Early reflections, late reflections and reverberation. My effort is to work with the early reflections of the sound trying to establish and build up an intense sonic environment both in the meaning of the sound itself, and additionally, in how the sound is being amplified when played inside such a reverberant space like a church or a cathedral. The sound works in an indirect way inside churches, cathedrals or auditoriums. The loudspeakers illuminate the entire view of the room/hall but only a tiny fraction 1/5th of 1% of the sound actually hits the target [the human ears in performance situation], the “direct sound”.

“Direct sound” refers to the notion of trying to create field of sounds which spread less than most traditional loudspeakers. One method of creating directivity utilizes very large arrays of loudspeakers, all driven together in-phase. This creates a very large source size compared to wavelength, and the resulting sound field is narrowed. The rest of the sound, over 99.8% of it, the “indirect sound”, misses the ears continuing on, crashing into the walls, floor, the people, chairs, the roof and its beams, the walls, windows and doors. Every time some part of the indirect sound hits a surface, it is reflected. How the surfaces of the hall reflect the indirect sound determines how the room sounds, its voice. And this is also depending on the material that has been used to construct the interior building surface. It is important to mention that, in all wave producing sources, the directivity of any beam, at maximum, corresponds to the size of the source compared to the wavelengths it is generating. The larger the source is compared to the wavelength of the sound waves, the more directional beam results. Sound waves have dimensions of inches to many feet, which is approximately the size of most loudspeaker systems. At high frequencies, however, the wavelengths are quite short, which can result in a narrow distribution of sound from the tweeters in a conventional loudspeaker system. What happens to the reflections of the indirect sound is the challenge for me here and it is what I would like to be focused on.

I want to use the building as a post-loudspeaker. The amount of indirect sound that is reflected depends on the acoustic nature of the reflecting surface. The indirect sound remains in the hall reflecting off of one surface after another, remaining audible to the listeners until it finally disappears, having been absorbed and leaked out of the room. There are two ways to make sound “louder”. The ordinary way is to make it physically louder. Not all reflections help hearing but those that do help people understand what they are hearing are called early reflections. Adding early reflections raises the apparent loudness of the direct sound in a comfortable, natural way, much more agreeable than turning up the volume. On the other hand, a good example of a late reflection is echo because it is a reflection that can be distinguished as being separate from the direct signal.

In “Hz vs Church” I would like to avoid dealing up with late reflections. The main reason is that my effort is to create an intense sonic environment in which the rapid cut-ups and the sudden changes in between the sounds are “cornerstones” in what I call “intensity”. Both in mental and listening procedure. In time speaking terms the cut-ups between the different sounds will happen at the very exact moment when I feel that the sound is getting deeper, at the very exact moment when layers are obviously getting denser and the hall is acoustically “filled up” and begin presenting its own “voice”. When I feel that the audience is ready to dive into the phenomena and spaces of sonic interest, when the time warns me up on this, then I cut it up and rapidly put the next sound. No fade ins, no fade outs. Just cut-ups.

Reverberation is a very common thing in big rooms or places like churches. Reverberation is not a series of echoes, like late reflections are. It is much more chaotic than that. Reverberation can come from somewhere but it is an overflow of chaotic sound being stored in a reverberant space. It is not a reflection of a sound wave. Reverberation is the proper term, when so many reflections arrive at a listener that he is unable to distinguish between them. Sabine’s reverberation equation was developed in the late 1890s in an empirical fashion. He established a relationship between the RT60 of a room, its volume, and its total absorption [in sabins]. This is given by the equation:

sabine

where c is a mathematical constant measuring 0.161, V is the volume of the room in m³, S total surface area of room in m², a is the average absorption coefficient of room surfaces, and Sa is the total adsorption in sabins. The total absorption in sabins [ and hence reverberation time ] generally changes depending on frequency [dependent on the which is defined by the acoustic properties of the space], and that the equation does not take into account room shape or dimensions, nor losses from the sound travelling through the air [important in big spaces like Cathedrals]. Generally, most rooms absorb less in the lower frequencies, causing a longer decay time.
In “Hz vs Church” the absorption, the decay time and the reverberation will change dramatically and rapidly between the different sounds and frequencies.
The reverberation time RT60 and the volume V of the room have great influence on the critical distance dc [conditional equation]:

sabine2

By using these different sounds and frequencies I want to generate a unique loudness for the direct sound and then compliment this with a bevy of early reflections, immediately followed by a distinct absence of late reflections and finally backfilled with a groundswell of distant sounding reverberation. The whole attempt is to present an exercise for the ears, to test the limit of the sound-gates in a room like a church and to figure out audience’s resistance, time-wise and listen-wise. We perceive a place with the ear and the eye. The eye perceives mainly material, when the ear perceives in a more conscious and concrete way.

“Hz vs Church” is not about mucical pleasure. The focus is on sound as an event and the explicit translation of sound in physical terms. It is about provoking new modes of perceiving and experiencing one’s own body and hearing by triggering variable and autonomous psycho-physiological responses. The major target is to create a multitude of effects in the audience, starting from high frequencies extreme mental intensity, and lead to the body’s great sway that low frequencies produce.

“Hz vs Church” is about the total acoustic sense of space, observing sound to control and measure the aural capacity of architecture by using material which, precisely, can be described as “audio assault”.

Posted April 26, 2008 in