Using Pressure and Gradient to Derive Microphone Patterns

Using Pressure and Gradient to Derive Microphone Patterns Audio Days 2011 Paris David Josephson Engineering, Inc. Santa Cruz, California

Scalars and Vectors • nondirectional/pressure/scalar – responds to pressure from any direction • directional/pressure-gradient/vector – responds to difference in pressure between two points

Pressure Response

Pressure Response

Pressure Gradient Response

Pressure Gradient Response

Cardioid pattern + =

What is B-Format? • • • signal format for Ambisonics W – omnidirectional (pressure) X – figure-8 (cos ) facing front-to-back Y – figure 8 facing side-to-side Z – figure 8 facing up-to-down

Native B-format • • omnidirectional mic produces W signal front-facing bidirectional mic produces X side-facing bidirectional mic produces Y (optional) up-down mic for Z

Set pattern with ratio of W to X a + b cos( ) a. . . is how much of the omni (W) b. . . is how much of the fig-8 (X)

+ = X + Y = another figure-8. . . pointed at an angle corresponding to the ratio of X and Y

5. 1 from B-format • • • FC = a. W + b. X (where a/b sets pattern) FL = a. W + b. X + c. Y FR = a. W + b. X - c. Y SL = a. W - b. X + c. Y SR = a. W - b. X - c. Y LFE = low passed W

Josephson C-700 S

Y W X

Billy Pitrone – guitar and vocal Sarah Eblin – bass and vocal Pete Hicks – fiddle, mandolin and vocal Rob Horgan – banjo Recorded by Dave Nielsen at Rancho Armadillo, Santa Cruz www. beancreekbluegrass. com

Anna Clyne, rewind Cabrillo Music Festival Orchestra, Marin Alsop, director Recorded by Cuco Daglio www. cabrillomusic. org