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Class Number: 381 Class Title: ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES Subclass Subclass Number Title 1 BINAURAL AND STEREOPHONIC 2 .Broadcast or multiplex stereo 3 ..FM final modulation 4 ...AM subcarrier 5 ....Four discrete channels 6 .....Having transmitter 7 ....Switch-type detector or modulator 8 .....Two diodes 9 .....Four or more diodes 10 ....Channel seperation control 11 ....Automatic switchover between mono and stereo modes 12 ....Stereo indicators (e.g., stereo presence) 13 ....Antinoise 14 ....Having transmitter 15 ..AM or both AM and angle final modulation 16 ...Having transmitter 17 .Pseudo stereophonic 18 ..Pseudo quadrasonic 19 .Quadrasonic 20 ..Matrix 21 ...4-2-4 22 ....Variable decoder 23 ....With encoder 23.1 .Hearing aid 24 .Speaker arrangement 25 ..Earphone 26 .Stereo sound pickup device (microphone) 27 .Center channel 28 .Amplifier 29 AUDIO BANDWIDTH COMPRESSION OR EXPANSION 30 .With content reduction encoding 33 .Delay line 34 TIME COMPRESSION OR EXPANSION (E.G., RUN LENGTH CODING) 35 .With content reduction encoding 36 SPEECH ANALYSIS AND SYNTHESIS COMBINED 37 .Using frequency 38 ..Pitch 39 ..Formants 40 .Using time 41 SPEECH ANALYSIS (E.G., PHONEME RECOGNITION) 42 .Voice recognition 43 .Word recognition 44 ..Phonetic typewriters 45 ..Frequency domain 46 .Detection of speech in noise 47 .Signal to noise ratio enhancement 48 .Speech parameter display 49 .Speech pitch fundamental frequency 50 .Speech formant frequencies 51 SPEECH SYNTHESIS 52 .Speech from printed matter 53 .Vocal tract modell 54 HELIUM SPEECH 55 AUDIO TRANSDUCER PROTECTION CIRCUITRY 56 MONITORING OF SOUND 57 .Amplification control responsive to ambient sound 58 MONITORING/MEASURING OF AUDIO DEVICES 59 .Loudspeaker operation 60 .Testing of hearing aids 61 SOUND EFFECTS 62 .Tremelo or vibrato effects 63 .Reverberators 64 ..Mechanical (e.g., reverberation chamber) 65 ...Helical spring 66 DEREVERBERATORS 67 STETHOSCOPES, ELECTRICAL 68 HEARING AIDS, ELECTRICAL 68.1 .Directional 68.2 .Frequency control 68.3 .Bone conduction 68.4 .Gain control 68.5 .Spectacle 68.6 .Ear insert 68.7 .Hook over ear 69 .Specified casing or housing 69.1 ..Having vacuum tube amplifier 69.2 ..Having battery 70 ARTIFICIAL LARYNX, ELECTRICAL 71 ACOUSTICAL NOISE OR SOUND CANCELLATION 72 HEARING PROTECTORS, ELECTRICAL 73.1 SOUND OR NOISE MASKING 74 HEADPHONE CIRCUITS 75 MEGAPHONES 76 LECTERNS 77 ONE-WAY AUDIO SIGNAL PROGRAM DISTRIBUTION 78 .Drive-in 79 .Near field 80 .Multiple channel 81 ..With switching 82 .Public address system 83 ..Feedback suppression 84 ..Spare amplifier substitution 85 ..Speaker or channel switching 86 VEHICLE 87 HAVING NON-ELECTRICAL FEATURE (E.G., MOUNTING) 88 .Having enclosure or housing 89 ..With loudspeakers driven in given phase relationship 90 ..With loudspeaker (e.g., baffle, spatial orientation, etc.) 91 ..With microphone 92 DIRECTIVE CIRCUITS FOR MICROPHONES 93 FEEDBACK SUPPRESSION 94 NOISE SUPPRESSION 95 MICROPHONE FEEDBACK 96 LOUDSPEAKER FEEDBACK 97 INCLUDING PHASE CONTROL 98 INCLUDING FREQUENCY CONTROL 99 .Having crossover filter 100 ..With active device 101 .Automatic tone control 102 ..With amplitude controll 103 .Having automatic equalizer circuit 104 INCLUDING AMPLITUDE OR VOLUME CONTROL 105 .Remote 106 .With amplitude compression/expansion 107 .Automatic 108 ..Including feedback 109 .With manual volume control 110 VOICE CONTROLLED 111 CIRCUITRY COMBINED WITH SPECIFIC TYPE MICROPHONE OR LOUDSPEAKER 112 .With carbon microphone 113 .With electrostatic microphone 114 .With piezoelectric microphone 115 .With magnetic microphone 116 .With electrostatic loudspeaker 117 .With magnetic loudspeaker 118 WITH MUSICAL INSTRUMENT 119 WITH MIXER 120 WITH AMPLIFIER 121 .Feedback 122 HAVING MICROPHONE 123 SWITCHING 150 ELECTRO-ACOUSTIC AUDIO TRANSDUCER 151 .Body contact wave transfer (e.g., bone conduction earphone, larynx microphone) 152 .Driven diverse static structure (e.g., wall, sounding board) 153 .With acoustic wave modifying structure 154 ..Including sound conducting tube 155 ..Directional 156 ..Sound intensifying or spreading element (e.g., horn) 157 ...Mouthpiece 158 ..Absorbing or attenuating element (e.g., baffle, obstruction, damping) 159 ..Enclosure or resonant cavity 160 ..Reflecting element 161 .With mechanical amplifier arrangement 162 .Detail of mechanical vibration coupling to transducer (e.g., tuned vibrating element) 163 .Having bi-directional transducer 164 .Thermal response to, or generation of, sound vibration 165 .By modifying fluid flow 166 .Having a fluid as a conducting element 167 ..Ionized gap, spark, or flame 168 .Microphone 169 ..With mounting or support feature 170 ..Compound 171 ..Micromagnetic 172 ..Light modifying 173 ..Piezoelectric or ferroelectric 174 ..Capacitive 175 ..Semiconductor junction microphone 176 ..Conductive diaphragm (e.g., reed, ribbon) 177 ..Dynamic (e.g., magnetic) 178 ..Vibrating electrical contract 179 ..Resistive 180 ...Granular or carbon 181 ....Differential 182 .Plural or compound reproducers 183 ..Headphonee 184 ..Different types of diaphragms 185 ..Having common voice coil 186 ..Plural diaphragms 187 .Having body supported structure (e.g., earphone) 188 .With mounting or support feature 189 .Having protective or sheilding feature 190 .Electrostrictive, magnetostrictive, or piezoelectric 191 .Having electrostatic element (e.g., electret, vibrating plate) 192 .Electromagnetic (e.g., dynamic) 193 ..Having feature of edge-supported diaphragm 194 ..Movable voice coil 195 ...Multiple (e.g., double) 196 ...Pattern 197 ...Centering 198 ..Including adjustment mechanism 199 ..Magnetic circuit or core structure 200 ...Armature 201 ...Magnetic configuration (e.g., tubular or U-shaped) 202 ..Specified diaphragm shape or structure 203 ...Flat 204 ...Conical 205 .Electro-acoustical transducer mounting or support 124 MISCELLANEOUS