This paper considers the Problem of altering a quiescent design for an arra
y of omni-directional sensors so that the altered design rejects afar-field
broadband signal from a given direction. This problem occurs where microph
one arrays are to be used to acquire speech signals for telecommunication a
nd interferring signals must be rejected. Three main results are presented
in this paper. First, conditions for imposing an exact broadband null upon
any given quiescent array response are,derived. Second, an analysis of the
sensitivity of exact nulling array responses to sensor position error is pr
esented. Third, frequency domain formulations for broadband nulls are obtai
ned and it is shown that these are less restrictive than the exact null con
ditions which are imposed in the time domain. A Lagrange multiplier approac
h is used to impose the null conditions upon a quiescent array response to
minimize the square error between the quiescent and nulled responses. A des
ign example is given. (C) 1999 Acoustical Society of America. [S0001-4966(9
9)02706-X].