Loudspeaking telephone station including directional microphone

A loudspeaking telephone station comprising:

• microphone apparatus for converting audible sounds into electrical signals, a loudspeaker for converting electrical signals into audible sounds, and a speech network that electrically connects the microphone apparatus and the loudspeaker to a telephone line, the microphone apparatus having a directional polar response characteristic such that the microphone apparatus is more sensitive to sounds emanating from one direction than from other directions,
• characterized in that:
• the polar response characteristic of the directional microphone includes a major lobe, one or more side lobes, and nulls between pairs of lobes, said major lobe having substantially greater amplitude than any of the side lobes;
• the loudspeaker is located at the center of the telephone station and positioned in the null of said polar response characteristic that resides between the major lobe and an adjacent side lobe;
• the loudspeaker is aimed in a first direction and the microphone apparatus is positioned so that its major lobe is aimed in a second direction, said first and second directions being approximately orthogonal;
• the microphone apparatus comprises four first-order-gradient (FOG) microphones that are positioned around an outside surface of the telephone station, each FOG microphone including sound ports on opposite sides of a common diaphragm that are separated by distance "d," and each FOG microphone is characterized by a free field directivity pattern, D(.theta.), that is given by:
• ##EQU3## where:
• B>1.

A loudspeaking telephone station comprising:

• microphone apparatus for converting audible sounds into electrical signals, a loudspeaker for converting electrical signals into audible sounds, and a speech network that electrically connects the microphone apparatus and the loudspeaker to a telephone line, the microphone apparatus having a directional polar response characteristic such that the microphone apparatus is more sensitive to sounds emanating from one direction than from other directions,
• characterized in that:
• the polar response characteristic of the directional microphone includes a major lobe, one or more side lobes, and nulls between pairs of lobes, said major lobe having substantially greater amplitude than any of the side lobes;
• the loudspeaker is positioned in the null of said polar response characteristic that resides between the major lobe and an adjacent side lobe;
• the loudspeaker is aimed in a first direction and the microphone apparatus is positioned so that its major lobe is aimed in a second direction, said first and second directions being approximately orthogonal;
• and
• the microphone apparatus comprises three second-order-gradient (SOG) microphones that are positioned around an outside surface of the telephone station and, each SOG microphone comprising a pair of collinear first-order-gradient (FOG) microphones.

A loudspeaking telephone station comprising:

• microphone apparatus for converting audible sounds into electrical signals, a loudspeaker for converting electrical signals into audible sounds, and a speech network that electrically connects the microphone apparatus and the loudspeaker to a telephone line, the microphone apparatus having a directional polar response characteristic such that the microphone apparatus is more sensitive to sounds emanating from one direction than from other directions,
• characterized in that:
• the polar response characteristic of the directional microphone includes a major lobe, one or more side lobes, and nulls between pairs of lobes, said major lobe having substantially greater amplitude than any of the side lobes;
• the loudspeaker is positioned in the null of said polar response characteristic that resides between the major lobe and an adjacent side lobe;
• the loudspeaker is aimed in a first direction and the microphone apparatus is positioned so that its major lobe is aimed in a second direction, said first and second directions being approximately orthogonal;
• and
• the microphone apparatus comprises a pair of collinear first-order-gradient (FOG) microphones separated by distance d.sub.1, each FOG microphone generating an electrical signal that is connected to a different input of a subtracting circuit, one of the electrical signals being delayed by a time interval .tau.;
• whereby a second-order-gradient polar response characteristic is achieved.