Onboard audio system and signal processing method therefor

The present invention relates to an in-vehicle audio device mounted on an automobile and a signal processing method thereof.

Although the interior of an automobile is soundproofed with a sound insulating material or the like, various noises such as engine noise, tire noise, and wind noise are still generated while driving. This noise changes variously depending on the driving conditions such as the running speed and the engine speed. Therefore, there is a problem that the audio signal of an in-vehicle audio device such as a car stereo is masked by noise and can be heard even if the volume is appropriate when the vehicle is stopped. On the contrary, there is a problem that the volume is too loud when the vehicle is stopped even if the volume is moderate when the vehicle is running at high speed.

Therefore, conventionally, in-vehicle audio devices that automatically adjust the volume and the like according to the running state of an automobile have been proposed (for example, Patent Document 1 and Patent Document 2).

Patent Document 1 detects a vehicle speed pulse indicating the traveling speed of an automobile and adjusts the output of a subwoofer for bass output according to the traveling speed. Further, in Patent Document 2, the volume is controlled according to the engine speed.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-23495</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2000-307366</text></patcit>

<p> However, both of Patent Documents 1 and 2 simply control the volume according to the vehicle speed and the engine speed. Therefore, it is appropriate according to the noise generation situation in the vehicle interior in various driving situations (for example, when the vehicle speed is slow but the engine speed is high on the uphill, or when the engine speed is low but the vehicle speed is high on the downhill). There was a problem that it could not be controlled.</p><p> Also, since it is a control that only adjusts the volume (even if the bass, treble and band are limited), it only makes the sound louder overall and makes it easier to hear the range masked by noise. Instead, there was a problem that the intelligibility and intelligibility did not improve even though the volume became louder.</p><p> An object of the present invention is to provide an in-vehicle audio device capable of easily hearing and controlling an audio signal under any driving situation and a control method thereof.</p>

<p> The invention according to claim 1 comprises a plurality of sensors for detecting a driving situation of an automobile, a noise estimation means for estimating noise in the vehicle interior at that time based on the detection values of the plurality of sensors, and the noise estimation. It is characterized by including a means for determining an equalization characteristic so that the audio signal is not masked by noise estimated by the means, and a signal processing unit for inputting an audio signal and performing signal processing with the determined equalization characteristic. And.</p><p> In the present invention, the noise in the vehicle interior at that time is estimated based on the detection values of a plurality of sensors that detect the driving situation. By estimating the noise based on the detection value of the sensor that detects the driving situation in this way, a microphone is provided to collect the sound in the vehicle interior, and the audio signal is separated from this audio signal to extract only the noise component. Further, processing such as frequency analysis becomes unnecessary, and noise detection (estimation) processing can be simplified. Then, the equalization characteristic is determined so that the audio signal is not masked by this noise. By equalizing the audio signal with this characteristic, it is possible to output the audio signal in an easy-to-hear manner without making it too loud under any driving situation.</p><p> The invention according to claim 2 further includes a noise database that stores noise characteristics corresponding to the plurality of sensors, and the noise estimation means obtains noise characteristics corresponding to the detection values of the plurality of sensors from the noise database. It is characterized in that noise is estimated by reading.</p><p> The present invention includes a noise database that stores noise characteristics in the vehicle interior. The noise characteristic is data representing the frequency spectrum of noise. Read the noise characteristics from the noise database based on the sensor detection values. This makes it possible to further simplify the noise estimation process.</p><p> According to the third aspect of the present invention, the plurality of sensors are a rotation speed sensor for detecting the engine rotation speed and an accelerator opening angle sensor for detecting the accelerator opening angle, and the noise database is one of the noises in the vehicle interior. It is an engine noise database that stores the engine noise characteristics of the engine noise component, and the noise estimation means estimates noise by reading out the engine noise characteristics corresponding to the detection values of the rotation speed sensor and the accelerator opening angle sensor. It is characterized by.</p><p> In the present invention, the engine noise characteristic of the engine noise component is read out based on the engine speed and the accelerator opening angle. Noise is estimated from this engine noise characteristic.</p><p> According to the fourth aspect of the present invention, the plurality of sensors are a rotation speed sensor for detecting the engine rotation speed, an accelerator opening angle sensor for detecting the accelerator opening angle, and a vehicle speed sensor for detecting the speed of the automobile, and the noise. The database consists of an engine noise database that stores the engine noise characteristics of the engine noise component of the noise in the vehicle interior and a driving noise database that stores the driving noise characteristics of the driving noise component of the noise in the vehicle interior. The noise is further provided with a synthesis means for generating noise characteristics in the vehicle interior by synthesizing the engine noise characteristics corresponding to the detection values of the number sensor and the accelerator opening angle sensor and the running noise characteristics corresponding to the detection values of the vehicle speed sensor. The estimation means is characterized in that noise is estimated by reading out the noise characteristics synthesized by the synthesis means.</p><p> In the present invention, the running noise characteristic of the running noise component is further read out based on the speed of the automobile and combined with the engine noise characteristic to generate the noise characteristic in the vehicle interior. Estimate the noise from the generated noise characteristics.</p><p> According to the fifth aspect of the present invention, the plurality of sensors are a rotation speed sensor for detecting the engine rotation speed and an accelerator opening angle sensor for detecting the accelerator opening angle, and the noise database is one of the noises in the vehicle interior. It is an engine noise database that stores the engine noise characteristics of the engine noise component, and the noise estimation means reads out the engine noise characteristics corresponding to the detection value of the rotation speed sensor and filters corresponding to the detection value of the accelerator opening angle sensor. It is characterized in that noise is estimated by the noise characteristics obtained by filtering the engine noise characteristics by the characteristics.</p><p> In the present invention, the engine noise characteristic of the engine noise component is read out based on the accelerator opening angle. In addition, the engine noise characteristics are filtered based on the engine speed. For example, even if the accelerator opening angle is large, if the engine speed is small, filtering is performed so that the volume of noise characteristics becomes small.</p><p> The invention according to claim 6 further includes a detection value averaging means for averaging the detection values of the plurality of sensors at predetermined time intervals, and the noise estimation means is averaged by the detection value averaging means. It is characterized in that noise is estimated based on the detected value.</p><p> In the present invention, the sensor detection values are averaged at predetermined time intervals. Estimate noise based on averaged detections. By averaging in this way, the audio signal can be changed more naturally without suddenly changing the volume.</p><p> The invention according to claim 7 is a storage means for storing a plurality of sensors for detecting a driving situation of an automobile and an equalization characteristic for avoiding masking due to noise in the vehicle interior estimated from the detection values of the plurality of sensors. It is characterized by including a signal processing unit that inputs an audio signal and performs signal processing with equalization characteristics read from the storage means in response to detection values of the plurality of sensors.</p><p> In the present invention, for a combination of various detected values of a plurality of sensors, a process of estimating the noise in the vehicle interior at that time and determining the equalization characteristic so that the audio signal is not masked by the estimated noise is performed in advance. The equalization characteristic obtained by this is stored in the storage means. When the in-vehicle audio device is in operation, the equalization process can be performed by reading out the equalization characteristics based on the detection values of a plurality of sensors, and the process in the device can be further simplified.</p><p> According to the invention of claim 8, the plurality of sensors include a rotation speed sensor for detecting the engine rotation speed, an accelerator opening angle sensor for detecting the accelerator opening angle, and a part or all of the vehicle speed sensor for detecting the speed of the automobile. is there.</p><p> In the present invention, the sensors are a rotation speed sensor that specifically detects the engine rotation speed, an accelerator opening angle sensor that detects the accelerator opening angle, and a vehicle speed sensor that detects the speed of the automobile. Provide some or all of these.</p><p> The invention according to claim 9 is a step of estimating the noise in the vehicle interior at that time based on the detection values of a plurality of sensors that detect the driving situation, and equalizing characteristics so that the audio signal is not masked by the estimated noise. It is characterized by having a step to determine.</p><p> The invention according to claim 10 corresponds to a step of storing an equalization characteristic for avoiding masking due to noise in the vehicle interior estimated by detection values of a plurality of sensors that detect a driving situation, and detection values of the plurality of sensors. It is characterized by having a step of reading out the equalization characteristic to be performed and determining the equalization characteristic.</p>

<p> As described above, according to the present invention, the noise in the vehicle interior is estimated according to the driving conditions detected by the plurality of sensors, and the audio signal is equalized so as not to be masked by the noise. Therefore, the vehicle speed and the engine speed are simply increased. It is possible to improve the intelligibility and intelligibility without excessively changing the volume as compared with raising or lowering the volume according to the above.</p>

FIG. 1 is a block diagram of an in-vehicle audio device according to an embodiment of the present invention. The control unit 10 is composed of a microprocessor, and has a built-in ROM for storing programs and databases, RAM for work memory, and various interfaces in addition to the CPU. As sensors for detecting the driving situation, a rotation speed sensor 20 for detecting the rotation speed of the engine, an accelerator opening angle sensor 21 for detecting the opening angle of the accelerator, and a vehicle speed sensor 22 for detecting the speed of the automobile. Is connected to the control unit 10 via the interface 16. Interface 16 shall have an A / D converter built-in if necessary. Further, in the case of an encoder in which the rotation speed sensor 20 and the vehicle speed sensor 22 output pulses according to the rotation of the engine or the rotation of the axle, the control unit 10 controls the rotation speed of the engine based on the integrated value of the pulses or the pulse interval. Or the vehicle speed may be calculated.

The control unit 10 periodically reads the detected values of the rotation speed sensor 20, the accelerator opening angle sensor 21, and the vehicle speed sensor 22, and estimates the current noise in the vehicle interior based on the detected values. This noise frequency characteristic is estimated by searching a noise estimation database that stores the noise characteristic, which is data representing the shape of the noise frequency spectrum, at each sensor detection value. Based on the estimated noise frequency characteristics, the equalization characteristics for the audio signal are determined so that the audio signal is not masked by this noise. When determining the equalization characteristic, instead of estimating the noise frequency characteristic, the masking characteristic due to noise in consideration of the human auditory characteristic may be obtained before calculating the equalization characteristic. In this case, the masking characteristic database is searched by the detected value of each sensor, and the equalization characteristic is determined so that the audio signal can be heard while avoiding the read masking characteristic. The determined equalization characteristics are output to DSP11, which is an equalizer. The noise characteristic stored in the noise estimation database may be waveform data as long as it is data representing the shape of the frequency spectrum, or may be a parameter that approximates the shape. As the waveform data, for example, plot data of a predetermined frequency interval on the frequency axis may be stored, and as the parameter, for example, data showing a polynomial (function) that approximates the shape of the frequency spectrum may be stored. You just have to keep it.

A digital audio signal is input to the DSP 11 from the audio source 12. The DSP 11 equalizes this audio signal with the equalization characteristics input from the control unit 10. The audio signal output from the DSP 11 is input to the audio circuit 13. The audio circuit 13 has a built-in D / A converter and an audio amplifier, D / A-converts the input audio signal, amplifies it, and outputs it from the speaker 14 embedded in the vehicle interior wall surface.

Therefore, the audio signal output from the speaker 14 is equalized in response to the noise in the vehicle interior, and the clarity and intelligibility of the audio signal should be increased without increasing the overall volume even during high-speed driving. Can be done.

FIG. 2 is a diagram showing the configuration of the noise estimation database. Further, FIG. 3 is a diagram showing a processing procedure of the control unit 10. In FIG. 2, the noise estimation database consists of a running noise database and an engine noise database. The driving noise database contains driving noise (noise propagating from the road surface and tires excluding engine noise, wind noise, etc.) at each vehicle speed step of 10, 20, 30, 40, 50, 60, 80, 100 (km / hour). The frequency characteristics of noise) are stored. In addition, the engine noise database has 0, 20, 40, 60, 80, 100 (%) accelerator opening steps and 1000, 2000, 3000, 4000, 5000, 6000 (rpm) engine speed steps, respectively. The frequency characteristics of the engine noise in the case of the combination of are stored.

For these noise frequency characteristics, the time average of the frequency characteristic data measured by actually driving the vehicle may be used, but in normal driving, it is necessary to separate the driving noise and the engine noise from the measured noise. is there. In order to measure the running noise and the engine noise separately in advance, the running noise may be measured by the towed vehicle without starting the engine, and the running noise may be measured by running on the chassis dynamometer device. Further, the running noise and the engine noise may be separated more accurately by comparing these measurement results with the measurement results during actual running. In addition, simulation results, wind tunnel measurement results, and the like may be taken into consideration.

In FIG. 3, the detected values of the engine speed sensor 20, the accelerator opening angle sensor 21, and the vehicle speed sensor 22 are read (s1), and the noise estimation database of FIG. 2 is searched with the detected values to find the corresponding noise frequency characteristics. Read (s2). In this reading, if the detected vehicle speed, accelerator opening angle, and engine speed do not match the above steps, rounding to one of the steps is performed. For example, when the vehicle speed is 47 km / h, the traveling noise frequency characteristic of 50 km / h is read out by rounding. When the accelerator opening angle is 15% and the engine speed is 2300 rpm, the nearest engine noise frequency characteristic of 20% x 2000 rpm is read out. In s3, the noise in the vehicle interior at that time is estimated by synthesizing the read running noise frequency characteristic and the engine noise frequency characteristic. In s3, the process of estimating the noise in the vehicle interior from only the engine noise frequency characteristic may be performed.

Further, the detected value of the sensor may be read after averaging at a predetermined time interval instead of reading in real time. Read the corresponding noise frequency characteristics based on the averaged detection values. By averaging in this way, the audio signal can be changed more naturally without suddenly changing the volume.

In the above example, the engine noise frequency characteristics corresponding to the detected values of the engine speed sensor 20 and the accelerator opening angle sensor 21 are read out, but the present invention is not limited to this example. The engine noise database stores the engine noise frequency characteristics corresponding to the detected values of the engine speed sensor 20, and filters the read engine noise frequency characteristics with the filter characteristics corresponding to the detected values of the accelerator opening angle sensor 21. May be good. This filter characteristic may be read from a database that stores the filter characteristic corresponding to the detection value of the accelerator opening angle sensor, or may be calculated from the detection value of the accelerator opening angle sensor.

After that, the masking characteristics due to noise are calculated based on the estimated noise characteristics (s4). Here, we determine how the audio signal is masked by the estimated noise frequency characteristics. In the simplest case, the noise frequency characteristic may be used as the masking frequency characteristic as it is. Based on this masking characteristic (masking frequency characteristic), the equalization characteristic is determined so that the audio signal is not masked (s5). The simplest is the equalization characteristic, which has the same characteristic as the noise frequency characteristic and increases the gain of the audio signal.

In determining the masking characteristics, in addition to the noise characteristics, the frequency characteristics of human hearing, the masking characteristics of overtones, and the like may be taken into consideration. Further, in addition to the frequency masking characteristic based on the current noise characteristic, the temporal masking characteristic based on the past noise characteristic may be considered. Temporal masking is masking on the time axis. For example, if one sound stops and another sound is played for a short time, the subsequent sound is drowned out by the previous sound and becomes inaudible. Is. After detecting a high noise level, the gain of the audio signal is increased for a predetermined time so as not to be masked on the time axis.

In the equalization process, instead of increasing the gain in the frequency range where the noise level is high, increasing the gain in the frequency range where the noise level is slightly lower than in the frequency range where the noise level is high suppresses the overall volume and improves the clarity and intelligibility. Can be high. If the frequency range where the noise level is high is a low frequency, the equalization characteristics are adjusted in consideration of masking of frequencies higher than that frequency. On the other hand, when the frequency range where the noise level is high is a high frequency, the equalization characteristic is adjusted considering only the high frequency without considering the masking of the frequency lower than that frequency. This is because low frequency audio signals are less likely to be masked by high frequency noise. By doing so, it is possible to further suppress the overall volume and increase the intelligibility and intelligibility.

The equalization characteristics determined as described above are output to DSP11, and the audio signal input from the audio source is equalized (s6).

The above is an embodiment in which noise characteristics are estimated masking characteristics are calculated equalization characteristics are determined in real time according to the sensor detection value. The in-vehicle audio device of the present invention can be modified as follows.

That is, the noise characteristics are estimated, the masking characteristics are calculated, and the equalization characteristics are determined for all the combinations of the vehicle speed step, the accelerator opening angle step, and the engine speed step in advance, and the calculated equalization characteristics are calculated. The combination of the vehicle speed step, the accelerator opening angle step, and the engine speed step is stored in the memory as an equalization characteristic database. As a result, in the actual operation of this in-vehicle audio device, the equalization characteristics can be determined only by searching the database based on the sensor detection value. In this case, since it is difficult to consider the noise change in time series, it is preferable to set the equalization characteristic in consideration of only frequency masking.

FIG. 4 is a diagram showing an operation procedure of the processing unit that stores the equalization characteristic database. The detection values of the engine speed sensor 20, the accelerator opening angle sensor 21, and the vehicle speed sensor 22 are read (s11), the equalization characteristic database is searched by the combination of these sensor detection values, and the corresponding equalization characteristics are read out (s12). Then, this equalization characteristic is output to DSP11 (s13). As a result, the audio signal can be equalized with a simpler process than the process shown in FIG. The corresponding equalization characteristic database may be searched from the detected values of the engine speed sensor 20 and the accelerator opening angle sensor 21 without considering the detected values of the vehicle speed sensor 22.

<figref num="1">Block diagram of an in-vehicle audio device according to an embodiment of the present invention</figref><figref num="2">The figure which shows the structure of the noise estimation database of the in-vehicle audio equipment</figref><figref num="3">The figure which shows the processing procedure of the control part of the in-vehicle audio equipment</figref><figref num="4">The figure which shows another form of the processing procedure of the control part of the in-vehicle audio equipment.</figref>

Code description

10 ... Control 11 ... (Functions as an equalizer) DSP 12 ... Audio source 13 ... Audio circuit 14 ... Speaker 15 ... Operation unit 16 ... Interface 20 ... Engine speed Number sensor 21 ... Accelerator opening angle sensor 22 ... Vehicle speed sensor