Electrical device for reducing noise

Abstract

The electrical device for reducing noise comprises a first microphone (110) configured to receive sound waves from a sound source and convert the sound waves into a first electrical signal including a noise component, and a second microphone (112) configured to receive ambient noise from a surrounding environment and convert the ambient noise into a second electrical signal. The second electrical signal has an opposite polarity to the first electrical signal. The electrical device further comprises a circuit (113) connecting the first microphone (110) and the second microphone (112). The circuit (113) is configured to combine the first and second electrical signals to reduce the noise component in the first electrical signal using the second electrical signal of opposite polarity.

Description

Technical Field

[0001] The present disclosure generally relates to noise cancellation technology and noise reduction technology, and more specifically to an electrical device for reducing noise.

Background Art

[0002] Noise control or noise cancellation has long been used as a means to reduce unwanted sounds for personal comfort, environmental concerns, or compliance with regulations, and is implemented in many electronic and communication devices such as mobile phones, two-way radios / walkie talkies, microphones, headsets, speakers, etc. (For example, Patent Documents 1 to 3) The main purpose of this technology is to remove or reduce unwanted noise (such as environmental noise) so that only desired sounds such as human voices can be heard.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Ambient environmental noise during communication or voice recording causes interference with the communication or recording and makes effective transmission of the sound impossible. For example, during communication between users via a transceiver, the environmental noise may be louder than the user's voice or be large enough to interfere with the communication. As a result, neither user can be clearly heard.

[0005] Therefore, in the relevant technical field, it is necessary to develop an electrical device for reducing noise without the above-mentioned drawbacks, and at least to provide an effective and efficient alternative.

Means for Solving the Problem

[0006] The present disclosure will be described below by various embodiments. However, the present disclosure can be embodied in many different forms and should not be construed as being limited to the embodiments described herein.

[0007] An electrical device for reducing noise is provided. The electrical device includes a first microphone configured to receive sound waves from a sound source and convert the sound waves into a first electrical signal including noise components, the first microphone including a first positive terminal and a first negative terminal, and the first electrical signal being output from the first positive terminal; an electret microphone that receives environmental noise from the surrounding environment and is configured to convert the environmental noise into a second electrical signal having a polarity opposite to that of the first electrical signal, the electret microphone including a second positive terminal and a second negative terminal, the second electrical signal being output from the second negative terminal, and the second electrical signal having a polarity opposite to that of the first electrical signal; and a circuit connecting the first microphone and the second microphone. The circuit includes a second resistor connected to the second negative terminal of the second microphone, the second positive terminal of the second microphone being connected to the ground of the circuit, the second resistor generating a second bias for the second negative terminal of the second microphone, reducing the current flowing through the second microphone to reverse the polarity of the second electrical signal, and the circuit being further configured to synthesize the first electrical signal and the second electrical signal to reduce the noise components in the first electrical signal using the second electrical signal having the opposite polarity.

[0008] The second electrical signal representing environmental noise has the advantage of having an opposite polarity and being synthesized with the first electrical signal. According to the above, the noise components in the first electrical signal are significantly reduced, and the signal-to-noise ratio (SN ratio) of the synthesized signal becomes higher. As a result, the sound generated by the receiving device based on the synthesized signal becomes clearer to the user using the receiving device.

[0009] The first microphone is an unidirectional electret microphone, and the first negative terminal is connected to the ground of the circuit.

[0010] The second microphone is an omnidirectional electret microphone.

[0011] The circuit further includes a first capacitor connected between the first positive terminal of the first microphone and the ground of the circuit to filter out high-frequency current in the first electrical signal.

[0012] The circuit further includes a first resistor connected to the first positive terminal of the first microphone to generate a first bias voltage for the first positive terminal of the first microphone.

[0013] The circuit further includes a first inductor connected in series with the first resistor to prevent high-frequency interference.

[0014] The circuit further includes a second capacitor connected between the second negative terminal of the second microphone and the ground of the circuit to filter out high-frequency current in the second electrical signal.

[0015] The circuit further includes a second inductor connected in series with the second resistor to prevent high-frequency interference.

[0016] The circuit further includes an output terminal, and the first inductor and the second inductor are connected at the output terminal to synthesize the first electrical signal and the second electrical signal.

[0017] The circuit further includes a third resistor connected between the first negative terminal of the first microphone and the second positive terminal of the second microphone to prevent electromechanical feedback.

[0018] According to an embodiment of the present disclosure, the circuit further includes a switch connected in series with the third resistor.

Brief Description of the Drawings

[0019] At least one embodiment of the present invention will be described with reference to the accompanying drawings:

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0021] It should be noted that in the accompanying drawings and the following description, like or identical reference numerals in different drawings indicate the same or similar elements.

DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 shows a structural diagram of an electrical device 100 for reducing noise according to an embodiment of the present disclosure. As shown in FIG. 1, the electrical device 100 includes a first microphone (110), a second microphone (112), and a circuit (113). The first microphone (110) is arranged in the vicinity or direction of the sound source during use, and specifically, is configured to receive sound waves from the sound source. The sound source can be any object that generates a desired sound wave and is intended to be received by the first microphone (110). In the embodiment shown in FIG. 1, the sound source is a person speaking towards the first microphone (110). The sound waves from the sound source, that is, the human voice in this embodiment, are propagated to the first microphone (110) through a transmission medium, specifically air, and captured by the first microphone (110). Then, the first microphone (110) converts the sound waves into a first electrical signal. In reality, during the transmission of sound waves in the transmission medium, the sound waves of the sound source are interfered by at least a part of the environmental noise, and may be caused by other objects such as machines or vehicles operating nearby, other people speaking nearby, or echoes that are an even multiple of the desired sound wave. As a result, the first electrical signal converted by the first microphone (110) includes a noise component in addition to the human voice. In the embodiment shown in FIG. 1, the first electrical signal is output from the positive terminal of the first microphone (110).

[0023] As shown in FIG. 1, the second microphone (112) is arranged away from the sound source during use, receives environmental noise from the surrounding environment, and specifically, is configured to convert the environmental noise into a second electrical signal representing the environmental noise. The environmental noise includes any undesired sound generated in the surrounding environment, for example, traffic, honking cars, yelling, loud music, or any other undesired noise. In the embodiment shown in FIG. 1, the second electrical signal is output from the negative terminal of the second microphone (112) and has the opposite polarity to the first electrical signal.

[0024] The circuit (113) is configured to connect the first microphone (110) and the second microphone (112) and synthesize the first electrical signal and the second electrical signal. For example, the circuit 113 can be an addition circuit that adds the first electrical signal and the second electrical signal. As a result, the output signal generated in the circuit (113) is the sum of the first electrical signal and the second electrical signal. When the polarity of the second electrical signal is opposite to that of the first electrical signal, the noise component in the first electrical signal is reduced by the second electrical signal after the first electrical signal and the second electrical signal are added. Therefore, the signal-to-noise ratio (SNR) of the output signal generated in the electrical device (100) is higher than that of the first electrical signal including voice and noise. The output signal of the electrical device (100) can be further processed, for example, digitized (analog-to-digital conversion (AD conversion)), modulated, and transmitted to a receiving device. The receiving device generates a voice signal with a higher SNR from the received signal, for example, via demodulation and digital-to-analog conversion (DA conversion). When the voice signal is reproduced from the speaker of the receiving device, the user using the receiving device can hear the human voice more clearly because the SNR of the voice signal is further increased.

[0025] Figure 2 shows an electrical device 200 for reducing noise according to an embodiment of the present disclosure. The circuit (113) in the electrical device 200 has a ground or a negative electrode and establishes a connection between the first microphone (110) and the second microphone (112). The first microphone (110) in the electrical device (200) (i.e., the "voice mic" in Figure 2) is a unidirectional electret microphone including a first positive terminal and a first negative terminal. The first negative terminal is connected to the ground or the negative electrode of the circuit (113), and the first electrical signal measurable at point 1.01 in Figure 2 is output at the first positive terminal of the first microphone (110). A unidirectional microphone can capture sound waves from a specific direction while suppressing sounds from other directions. In one example, when the first microphone (110) receives an audio signal at an angle of 0 degrees, a minimal environmental signal is detected, allowing only signals from one direction to be received, and the low bandwidth filters out unwanted higher frequencies. Thus, when the first microphone (110) is directed towards the sound source, the sound waves received by the unidirectional microphone (110) are less interfered with by environmental noise, and the noise included in the resulting first electrical signal is further reduced. Finally, the output signal of the electrical device (200) is further improved and measurable at point 1.03 in Figure 2.

[0026] Furthermore, the second microphone (112) in the electrical device (200) is an omnidirectional electret microphone including a second positive terminal and a second negative terminal. As shown in Figure 2, the second positive terminal is connected to the ground of the circuit (113), and the second electrical signal measurable at point 1.02 in Figure 2 is output at the second negative terminal of the second microphone (112). An omnidirectional electret microphone receives sounds from all directions with substantially equal gain. Thus, the resulting second electrical signal can accurately represent environmental noise. Furthermore, the second electrical signal is output at the second negative terminal of the second microphone (112), and the second electrical signal has a polarity opposite to that of the first electrical signal output at the first positive terminal of the first microphone (110).

[0027] As shown in FIG. 2, the circuit (113) includes a first capacitor (114). The first capacitor (114) is connected between the first positive terminal of the first microphone (110) and the ground of the circuit (113). The first capacitor (114) is configured to filter out high-frequency currents in the first electrical signal, prevent sudden radio frequencies from being input into the low-frequency audio circuit (113), and prevent voltage spikes when the circuit (113) is closed. The first capacitor (114) can be a ceramic capacitor, and the capacitance of the first capacitor (114) can be, for example, 1 μF (microfarad). The circuit (113) further includes a first resistor (118) connected to the first positive terminal of the first microphone (110). The first resistor (118) can generate a first bias voltage for the first positive terminal of the first microphone (110), and the first resistor (118) can add a slight attenuation to the first electrical signal. The resistance value of the first resistor (118) can be, for example, 1.8 kΩ (kiloohm). The circuit (113) further includes a first inductor (122) connected in series with the first resistor (118). Although not shown in FIG. 2, when the electrical device (200) is integrated into a wireless device (such as a mobile phone), which is usually part of a wireless device that uses a radio frequency transmitter for transmitting radio frequency signals in the air, the first inductor (122) prevents high-frequency interference by suppressing the possibility that radio frequency interference generated by the transmitter is input into the low-frequency audio circuit (113). The inductance of the first inductor (122) can be, for example, 0.02 mH (millihenry).

[0028] The circuit (113) includes a second capacitor (116) connected between the second negative terminal of the second microphone (112) and the ground of the circuit (113). The second capacitor (116) is configured to filter out high-frequency currents in the second electrical signal, prevent sudden radio frequencies from being input into the low-frequency audio circuit (113), and prevent voltage spikes when the circuit (113) is closed. The second capacitor (116) can be a ceramic capacitor, and the capacitance of the second capacitor (116) can be, for example, 1 μF (microfarad). The circuit (113) further includes a second resistor (120) connected to the second negative terminal of the second microphone (112). The second resistor (120) generates a second bias voltage for the second negative terminal of the second microphone (112). Thus, the second resistor (120) enables the second microphone (112) (especially, the JFET transistor in the second microphone (112) when the second microphone (112) is an electret microphone) to operate in reverse polarity. The second resistor (120) further reduces the current passing through the second microphone (112) and the amplitude of the voltage in the second microphone (112). The resistance value of the second resistor (120) can be, for example, 1.8 kΩ (kiloohm). The circuit (113) further includes a second inductor (124) connected in series with the second resistor (120). The second inductor (124) is configured to prevent radio frequency interference generated by the wireless transmission device from being input into the low-frequency audio circuit (113). The inductance of the second inductor (124) can be, for example, 0.02 mh (millihenry).

[0029] The circuit (113) further includes an output terminal (201) connecting the first inductor (122) and the second inductor (124). In this way, the circuit (113) synthesizes the first electrical signal and the second electrical signal at the output terminal (201). The synthesized output signal, which is the sum of the first electrical signal and the second electrical signal, can be measured at point 1.03. As described above, the second electrical signal has the opposite polarity to the first electrical signal including noise components. Therefore, in the synthesized output signal, the noise components are reduced.

[0030] The electrical device (200) shown in FIG. 2 can be integrated as part of a wireless device (e.g., a mobile phone) when the wireless device is manufactured by the original manufacturer. For example, the output signal synthesized at the output terminal (201) can be supplied to other circuits of the wireless device for further processing (e.g., analog-digital conversion, modulation, encryption, transmission, etc.). The ground of the circuit (113) is connected to the ground of other circuits of the wireless device to electrically connect the electrical device (200) to other circuits of the wireless device. Thus, the electrical device (200) can be used for full-duplex applications such as mobile phones.

[0031] FIG. 3 shows an electrical device (300) for reducing noise according to an embodiment of the present disclosure. The electrical device (300) can be used as an accessory for an existing wireless device when there is no noise reduction function or when a better noise reduction function is desired.

[0032] As shown in FIG. 3, in addition to the elements shown in FIGS. 1 and 2, the circuit (113) in the electrical device 300 further includes a third resistor (126). The third resistor (126) is connected to the first negative terminal of the first microphone (110) and the second positive terminal of the second microphone (112), and is in fact connected to the ground of the circuit (113). Further, the circuit (113) includes a switch (128) connected in series with the third resistor (126) for the purpose of "push to talk". The third resistor (126) is configured to prevent electromechanical feedback from being input into the low-frequency audio circuit (113) when, for example, the switch (128) is pressed and closed. Electromechanical feedback may be generated when the electrical device (300) is used in a half-duplex communication mode. In one embodiment, the resistance of the third resistor (126) can be, for example, 0 Ω (ohm). Further, the circuit (113) includes a switch (128) connected in series with the third resistor (126) for the purpose of "push to talk". The electrical device (300) further includes a connector (130), and the electrical device (300), specifically the circuit (113), is configured to be connected as an accessory to an existing wireless device (for example, a transceiver not shown in FIG. 3) when there is no noise reduction function. For example, when a noise reduction function is desired, the connector (130) can be inserted into the wireless device to connect the electrical device (300) to the wireless device.

[0033] The switch (128) is connected to the connector (130) for the purpose of "push to talk". Further, the output terminal (201) of the electrical device (300) is connected to the connector (130) to supply a combined output signal, which is the sum of the first electrical signal and the second electrical signal, to a wireless device that performs further processing such as analog-digital conversation, modulation, encryption, transmission, etc. The electrical device (300) can supply a wireless device with an input signal having a higher SNR, that is, the combined output signal from the output terminal (201). In this way, when another wireless device, that is, a receiving wireless device, receives a signal from the wireless device and generates voice from the received signal, the voice of the person using the wireless device becomes clearer to the user using the receiving wireless device.

[0034] A wireless device, e.g., a transceiver / bidirectional radio, typically includes an internal speaker for playing audio generated by the wireless device. The electrical device (300) may further include a speaker (131) connected to a connector (130). The connector (130) is configured to disable the internal speaker of the wireless device and play the sound generated by the wireless device through the speaker (131) as an external speaker when the connector (130) is inserted into the wireless device.

[0035] The connector (130) in the embodiment shown in FIG. 3 is a two-pin connector. One pin is configured to connect to the speaker (131) and is labeled as the speaker pin, and the other pin is configured to control the microphones (110, 112) and is labeled as the microphone pin. The speaker pin of the connector (130) includes a positive terminal and a negative terminal / ground, and the microphone pin of the connector (130) includes a microphone terminal and a "press-to-talk" terminal. The speaker (131) includes a positive terminal and a negative terminal. The positive terminal of the speaker (131) is connected to the positive terminal of the speaker pin, and the negative terminal of the speaker (131) is connected to the negative terminal / ground of the speaker pin. The ground of the circuit (113) is connected to the negative terminal / ground of the speaker pin.

[0036] The microphone terminal of the microphone pin is connected to the output terminal (201) and receives a combined output signal with a higher SNR. The "pre-talk" terminal of the microphone pin is connected to the "pre-talk" switch (128) for "pre-talk" purposes. Thus, after the connector (130) is inserted into a wireless device (not shown), when the "pre-talk" switch (128) is pressed by the user using the electrical device (300), the circuit (113) becomes closed. Therefore, the first microphone and the second microphone (110, 112) can operate as described above, and the combined output signal with a higher SNR is output at the output terminal (201), further supplied to the connector (130), and then supplied to the wireless device before being transmitted to the receiving wireless device for further processing. On the other hand, when the "pre-talk" switch (128) is opened by the user, the combined output signal is not supplied to the connector (130) or the wireless device. As a result, the sound from the sound source is not transmitted to the receiving wireless device. Thus, the electrical device (300) can be used in a half-duplex device such as a two-way radio or transceiver.

[0037] The waveforms of the first electrical signal, the second electrical signal, and the combined output signal will be described below with reference to FIGS. 4, 5, and 6, showing the effects of the present disclosure.

[0038] FIG. 4 shows the waveform of the first electrical signal measured at point 1.01 in the electrical device (300) shown in FIG. 3. The frequency of the first electrical signal is about 1 KHz, and the voltage between peaks is 200 mV, i.e., 46 DbmV. As described above, the first electrical signal includes a desired sound (e.g., human voice) and a noise component.

[0039] Figure 5 shows the waveform of the second electrical signal measured at point 1.02 in the electrical device (300) shown in Figure 3. When the second microphone (112) operates with reverse polarity, the waveform of the second electrical signal is 180 degrees out of phase with the first electrical signal. In other words, the second electrical signal has the opposite polarity to the first electrical signal. The peak-to-peak voltage of the second electrical signal is 100 mV, i.e., 40 DbmV. As described above, the second electrical signal represents environmental noise.

[0040] Figure 6 shows the waveform of the combined output signal measured at point 1.03 in the electrical device (300) shown in Figure 3. As described above, the first electrical signal and the second electrical signal are combined, and the combined output signal is output at the output terminal (201). The combined output signal is the sum of the first electrical signal and the second electrical signal. As shown in Figure 6, the peak-to-peak voltage of the combined output signal is 100 mV, i.e., 40 DbmV, and due to the reverse polarity of the second electrical signal, it is lower than the peak-to-peak voltage of the first electrical signal.

[0041] The test shows that the SNR of the electrical device (300) reaches an SNR of 59 dB, while the SNR of existing wireless devices (e.g., transceivers) is stated to be approximately 40 dB by the manufacturers of the wireless devices. Therefore, the present disclosure achieves a better audio effect than existing wireless devices.

[0042] The advantages of the present disclosure are diverse. The present disclosure provides a cost-effective and energy-efficient approach to noise reduction / noise cancellation. The present disclosure can provide noise reduction / noise removal via a communication device. The devices of the present disclosure can be used with various communication devices such as mobile phones, radios, transceivers, satellite phones, etc.

[0043] The terms and descriptions used in this specification are provided for illustrative purposes only and are not meant to be limiting. The examples and limitations disclosed herein are not intended to limit in any way, and can be changed without departing from the spirit of the disclosure. Those skilled in the art will recognize that many modifications are possible within the spirit and scope of the disclosure and the scope of its equivalents, and that all terms should be understood in their broadest, most inclusive sense unless otherwise indicated.

[0044] Various changes to the above-described embodiments will be apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein can be applied to other embodiments. Accordingly, the above description is not intended to be limited to the embodiments shown with the accompanying drawings, but rather is intended to provide the broadest scope consistent with the principles disclosed or suggested herein and the novel and inventive features. Thus, the present disclosure preserves, prior to, all other alternative, modified, and variant forms of the present disclosure and the scope of the appended claims.

Claims

1. An electrical device for reducing noise, A first microphone (110) configured to receive sound waves from a sound source and convert the sound waves into a first electrical signal including noise components, the first microphone (110) including a first positive terminal and a first negative terminal, and the first electrical signal being output from the first positive terminal; A second microphone (112) configured to receive ambient noise from the surrounding environment and convert the ambient noise into a second electrical signal, the second microphone (112) being an electret microphone including a second positive terminal and a second negative terminal, the second electrical signal being output from the second negative terminal, and the second electrical signal having a polarity opposite to that of the first electrical signal; A circuit (113) connecting the first microphone (110) and the second microphone (112); comprising The circuit (113) includes a second resistor (120) connected to the second negative terminal of the second microphone (112), The second positive terminal of the second microphone (112) is connected to the ground of the circuit (113), The second resistor (120) generates a second bias for the second negative terminal of the second microphone (112), reduces the current flowing through the second microphone (112), and reverses the polarity of the second electrical signal, The circuit (113) is further configured to synthesize the first electrical signal and the second electrical signal to reduce the noise components in the first electrical signal using the second electrical signal with an opposite polarity. Electrical device.

2. The first microphone (110) is a unidirectional electret microphone, and the first negative terminal is connected to the ground of the circuit. The electrical device according to claim 1.

3. The second microphone (112) is an omnidirectional electret microphone. The electrical device according to claim 2.

4. The circuit (113) further includes a first capacitor (114) connected between the first positive terminal of the first microphone (110) and the ground of the circuit to filter out high-frequency current in the first electrical signal. The electrical device according to claim 3.

5. The circuit (113) further includes a first resistor (118) connected to the first positive terminal of the first microphone to generate a first bias voltage for the first positive terminal of the first microphone. The electrical device according to claim 4.

6. The circuit (113) further includes a first inductor (122) connected in series with the first resistor (118) to prevent high-frequency interference. The electrical device according to claim 5.

7. The circuit (113) further includes a second capacitor (116) connected between the second negative terminal of the second microphone (112) and the ground of the circuit to filter out high-frequency current in the second electrical signal. The electrical device according to claim 6.

8. The circuit (113) further includes a second inductor (124) connected in series with the second resistor (120) to prevent high-frequency interference. The electrical device according to claim 7.

9. The circuit (113) further includes an output terminal (201), and the first inductor and the second inductor are connected at the output terminal (201) to synthesize the first electrical signal and the second electrical signal. The electrical device according to claim 8.

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