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

Using Pressure and Gradient to Derive Microphone Patterns

Audio Days 2011

Paris

David Josephson

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 = aW + bX (where a/b sets pattern)

• FL = aW + bX + cY

• FR = aW + bX - cY

• SL = aW - bX + cY

• SR = aW - bX - cY

• LFE = low passed W

Josephson C-700S

W

X

Y

Billy Pitrone – guitar and vocal Sarah Eblin – bass and vocal Pete Hicks – fiddle, mandolin and vocalRob 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