Newsletter

This week we read another section of a soon-to-be-released white paper by Art Noxon, Acoustical Engineer, that bridges a few previously covered topics with a few that are upcoming. Enjoy!

Loudspeaker Directivity

Sound emanates from a loudspeaker with various loudness levels in various directions all of which varies with the frequency being played. For traditional speakers, the bass emanates with equal strength in all directions. This makes an omni or spherical sound pattern in the bass range. In the treble range sound is projected with equal strength forward and to all sides but rapidly tapers off in the rearward direction. It creates a forward-facing semispherical distribution of treble range sound, a cardioid sound pattern.

There are many other types of speakers and driver arrangements for speakers each of which produces a different sound distribution pattern. Whatever the pattern may be, they all illuminate the listener with a direct segment of the sound pattern. Most of the distribution pattern misses the listener and goes on to reflect off the surfaces and objects in the listening room. The listener hears an aggregate of the direct plus many reflections as the sound of the speaker, its musicality and imaging qualities of its sound.

Synesthesia

As we hear sound we form a sonic image of where the sound is coming from. We perceive the size of the sound source and its location. Sometimes this sonic image appears with an overlaid visual image, this visual image occurs where the sonic image is located, something like an image in a dream. This is a natural effect called synesthesia, acknowledged to exist in the audio world, simulated below.

The nerve pulses for processing sound in our mind are located near where the nerve pulses for processing sight in our mind is located. Some of the sound signals bleed into the visual sensory circuit and the result is a visual overlay of the sonic image. The language used to describe the perception of sonic imaging is the same language used to describe our perception of visual images.

Early Room Reflections

Stereo speakers playing a mono signal can produce a tight center image in a room that does not have strong early reflections. The tight center image is seen as a very bright, hot white, “dime sized” image. When the room begins to add off-axis early reflections to the direct signal, the hot white dime sized image begins to disappear, replaced by a larger but dimmer floating ball of fuzz. The more there are of early reflections, the larger and dimmer the ball of fuzz seems to grow.