Apparatus and method for actively reducing noise in vehicular passengers compartment

An active noise reducing apparatus for an automotive vehicle, comprising:

• air intake sound wave monitoring means, comprising an air flow meter disposed in an air intake system of a vehicular engine, for monitoring an air intake sound wave generated in the air intake system from air intake noise and outputting a detection signal representative of the air intake sound wave;
• sound wave characteristic setting means for setting a frequency, an amplitude, and a phase of a noise-reducing sound wave on the basis of said detection signal derived from said air intake sound wave monitoring means;
• sound wave generating means for generating the noise-reducing sound wave on the basis of the frequency, the amplitude, and the phase set by said sound wave characteristic setting means, and interfering with the air intake sound wave so as to reduce the air intake noise;
• and
• acoustic-to-electrical transducing means for generating a signal representative of a sound wave remaining after interference of the intake sound wave,
• said air intake sound wave monitoring means being disposed within an air intake duct of the air intake system of the vehicular engine, the air intake duct being located upstream of an engine throttle valve,
• said sound wave generating means comprising electrical-to-acoustic energy transducing means, disposed adjacent to an air cleaner of the intake air system, for converting an electric signal into a corresponding acoustic signal, and
• said sound wave characteristic setting means comprising:
• 1) analog-to-digital converting means for converting the electric signal derived from said acoustic-to-electrical energy transducing means into a corresponding digital signal;
• 2) sampling means for sampling the electric signal derived from said acoustic-to-electrical energy transducing means before the analog-to-digital conversion by said analog-to-digital converting means within a predetermined sampling window and storing the sampled electric signals sequentially into a memory as digital discrete data MQ.sub.n (n=1, 2, 3, . . . n);
• 3) engine revolution speed determining means for determining an engine revolution speed Ne on the basis of an output signal from an engine crankshaft angular displacement sensor;
• 4) setting means for setting a center frequency f.sub.0 from the engine revolution speed Ne which is correlated to a frequency of intake air pulsation;
• 5) frequency analyzing and filtering means for extracting frequency components of the output signal of the airflow meter in a predetermined frequency bandwidth with the center frequency f.sub.0 as a center;
• 6) phase controlling means for providing a phase deviation of .theta. for the extracted frequency components;
• and
• 7) converting means for converting the phase deviated frequency components into a corresponding electric signal, the electric signal being supplied to said electrical-to-acoustic energy transducing means.

An active noise reducing apparatus for an automotive vehicle, comprising:

• air intake sound wave monitoring means, disposed in an air intake system of a vehicular engine, for monitoring an air intake sound wave generated in the air intake system from air intake noise and outputting a detection signal representative of the air intake sound wave;
• sound wave characteristic setting means for setting a frequency, an amplitude, and a phase of a noise-reducing sound wave on the basis of said detection signal derived from said air intake sound wave monitoring means;
• sound wave generating means for generating the noise-reducing sound wave on the basis of the frequency, the amplitude, and the phase set by said sound wave characteristic setting means, and interfering with the air intake sound wave so as to reduce the air intake noise;
• and
• acoustic-to-electrical transducing means for generating a signal representative of a sound wave remaining after interference of the intake sound wave,
• said air intake sound wave monitoring means being disposed within an air intake duct of the air intake system of the vehicular engine, the air intake duct being located upstream of an engine throttle valve,
• said sound wave generating means comprising electrical-to-acoustic energy transducing means, disposed adjacent to an air cleaner of the intake air system, for converting an electric signal into a corresponding acoustic signal, and
• further comprising an airflow meter which is constructed and arranged in the intake air system of the vehicular engine so as to detect an intake air quantity Qa drawn into the engine, and wherein said sound wave characteristic setting means comprises:
• 1) analog-to-digital converting means for converting the electric signal derived from said acoustic-to-electrical energy transducing means into a corresponding digital signal;
• 2) sampling means for sampling the electric signal derived from said acoustic-to-electrical energy transducing means before the analog-to-digital conversion by said analog-to-digital converting means within a predetermined sampling window and storing the sampled electric signals sequentially into a memory as digital discrete data MQ.sub.n (n=1, 2, 3, . . . n);
• 3) engine revolution speed determining means for determining an engine revolution speed Ne on the basis of an output signal from an engine crankshaft angular displacement sensor;
• 4) setting means for measuring a period Tf.sub.Q of a variation in a detected intake air quantity Qa of the airflow meter and setting a center frequency f.sub.0 from the measured period Tf.sub.Q ;
• 5) frequency analyzing and filtering means for extracting frequency components of the output signal of the airflow meter in a predetermined frequency bandwidth with the center frequency f.sub.0 as a center;
• 6) phase controlling means for providing a phase deviation of .theta. for the extracted frequency components;
• and
• 7) converting means for converting the phase deviated frequency components into a corresponding electric signal, the electric signal being supplied to said electrical-to-acoustic energy transducing means.

An active noise reducing apparatus for an automotive vehicle, comprising:

• air intake sound wave monitoring means, disposed in an air intake system of a vehicular engine, for monitoring an air intake sound wave generated in the air intake system from air intake noise and outputting a detection signal representative of the air intake sound wave;
• sound wave characteristic setting means for setting frequency, an amplitude, and a phase of a noise-reducing sound wave on the basis of said detection signal derived from said air intake sound wave monitoring means;
• sound wave generating means for generating the noise-reducing sound wave on the basis of the frequency, the amplitude, and the phase set by said sound wave characteristic setting means, and interfering with the air intake sound wave so as to reduce the air intake noise;
• and acoustic-to-electrical transducing means for generating a signal representative of a sound wave remaining after interference of the intake sound wave,
• said air intake sound wave monitoring means being disposed within an air intake duct of the air intake system of the vehicular engine, the air intake duct being located upstream of an engine throttle valve,
• said sound wave generating means comprising electrical-to-acoustic energy transducing means, disposed adjacent to an air cleaner of the intake air system, for converting an electric signal into a corresponding acoustic signal, and
• further comprising an airflow meter which is constructed and arranged in a part of the engine intake air system which is located downstream of said electrical-to-acoustic energy transducing means so as to detect an intake air quantity Qa sucked into the engine and wherein said sound wave characteristic setting means comprises:
• 1) first analog-to-digital converting means for converting the electric signal derived from said acoustic-to-electrical energy transducing means into a corresponding digital signal;
• 2) first sampling means for sampling the electric signal derived from said acoustic-to-electrical energy transducing means before the analog-to-digital conversion by said first analog-to-digital converting means within a predetermined sampling window and storing the sampled electric signals sequentially into a first memory as first digital discrete data MR.sub.n (n=1, 2, 3, . . . n);
• 3) first frequency analyzing means for carrying out a Fourier transform for the stored n-th number of the first digital discrete data MR.sub.n to provide a first frequency power spectrum PS;
• 4) first filtering means for filtering frequency components in the first frequency power spectrum PS in a first predetermined frequency band so as to extract the frequency components in said first predetermined frequency band from the first power spectrum PS;
• 5) second analog-to-digital converting means for converting an output signal AFM from said airflow meter into a corresponding digital signal;
• 6) second sampling means for sampling the output signal AFM from said airflow meter within said predetermined sampling window before conversion of the output signal AFM into the digital signal by said second analog-to-digital converting means and storing the sampled output signal AFM of the airflow meter into a second memory as second digital discrete data MQ.sub.n (n=1, 2, 3, . . . n);
• 7) second frequency analyzing means for carrying out a Fourier transform for the stored n-th number of the second digital discrete data MQ.sub.n to provide a second frequency power spectrum PSQ;
• 8) second filtering means for filtering frequency components in a second predetermined frequency band so as to extract the frequency components in said second predetermined frequency band from the second frequency power spectrum PS2;
• 9) determining means for determining whether an amplitude of any one of the frequency components extracted by said second filtering means in the second frequency power spectrum PSQ which is the same frequency component as that of the frequency components extracted by said first filtering means in the first frequency power spectrum PS is smallest;
• 10) phase deviating means for providing a further phase deviation .DELTA..theta. for the frequency component in the first frequency power spectrum PS when said determining means determines that the amplitude of any one of the frequency components extracted by said second filtering means in the second frequency power spectrum PSQ which is the same frequency component as that of the frequency components extracted by said first filtering means in the first frequency power spectrum PS is not smallest and for providing a 180.degree. phase deviation for the frequency components in the first frequency power spectrum PS when said determining means determines that the amplitude of any one of the frequency components extracted by said second filtering means in the second frequency power spectrum PSQ which is the same frequency component as that of the frequency components extracted by said first filtering means in the first frequency power spectrum PS is smallest;
• and
• 11) synthesizing and converting means for synthesizing and converting the frequency components under phase deviation into a single electric signal, said electric signal being supplied to said electrical-to-acoustic energy transducing means.

An active air intake noise reducing apparatus for an automotive vehicle, comprising:

• an air intake signal generator for generating an air intake signal representative of an air intake quantity;
• a signal processor for generating a cancellation signal having a frequency, amplitude and phase for canceling the air intake signal;
• a sound wave generator for generating a cancellation sound wave in accordance with the cancellation signal to cancel an air intake sound wave;
• and
• a cancellation monitor for generating a monitor signal representative of a sound wave remaining after cancellation of the air intake sound wave by the cancellation sound wave,
• said signal processor including means for correcting said cancellation signal in accordance with said monitor signal, comprising:
• a sampler for sampling the monitor signal within a predetermined sampling window and for storing the sampled electric signals sequentially into a memory as discrete data MR.sub.n (n=1, 2, 3, . . . n);
• first frequency analyzing means for performing a Fourier transform for the stored n-th number of discrete data to provide a first frequency power spectrum (PS1):
• first filtering means for filtering frequency components in the first frequency Power spectrum PS1 to extract frequency components in a first predetermined frequency band;
• first phase control means for providing a phase deviation of a first predetermined angle .theta.1 for extracted frequency components in the first predetermined frequency band;
• second frequency analyzing means for performing a Fourier transform for the stored n-th number of discrete data MR.sub.n to provide a second frequency power spectrum (PS2);
• second filtering means for filtering frequency components in the second frequency power spectrum PS2 to extract frequency components in a second predetermined frequency band;
• second phase control means for providing a phase deviation of a second predetermined angle .theta.2 for the extracted frequency components in said second predetermined frequency band;
• and
• synthesizing means for synthesizing and converting each extracted frequency component into a correction electric signal and providing the correction signal to the sound wave generator.