1. Field of the Invention
The present invention relates to noise reduction headsets and method for designing the headsets, and more particularly to an active noise reduction headset and a method for designing the headset.
2. Description of related art
Presently acoustic products such as MP3, MP4 or music mobile phones are widely used in daily life. People always wear headsets for receiving sound signals from the acoustic products. However, there are external acoustic noises which interfere with the sound signals generated by the acoustic products and received from the headsets. This reduces the sound quality received by the users of the acoustic products.
Nowadays, an active noise control (ANC) system is used in the headsets for canceling the acoustic noises. There are two kinds of active noise reduction headsets, i.e., in-ear type headsets and ear-muff type headsets.
The in-ear type headset has a compact size and is more portable as compared with the ear-muff type headset. However, the in-ear type headset merely has an external microphone for receiving sound signals. This makes adaptive control methods such as the least-mean-square (LMS) algorithm be not able to be used in the in-ear type headset, which lowers the sound quality of the in-ear type headset.
The ear-muff type headset 10 as shown in
However, the ear-muff type headset 10 has two microphones, i.e. the external microphone 12 and the internal microphone 14, which respectively receive the external noise sound signals and the error noise sound signals. This makes the ear-muff type headset 10 occupy a large size and further have a higher cost. Therefore, there is a need to provide a headset 10 which has good noise reduction effect and has a compact size and low cost.
The present invention relates, in one aspect, to a noise reduction headset which has a good noise reduction effect but occupying a compact size. The noise reduction headset includes a pair of headphones each of which includes an ear cup, an external microphone, an internal loudspeaker, and a control unit connected between the external microphone and the internal loudspeaker. The external microphone receives external noise sound signals. The control unit has a preferred related function for converting the external noise sound signals from the external microphone into an anti-phased noise sound signals. The anti-phased noise sound signals are broadcasted by the internal loudspeaker The anti-phased noise sound signals interfere with and reduce the external noise sound signals entering the ear cup.
The present invention relates, in another aspect, to a method for designing the noise reduction headset. The method includes: providing an internal microphone disposed in the ear cup of the noise reduction headset, providing a transfer function between the external microphone and the internal microphone and storing the transfer function into a first filter, providing a transfer function between the internal loudspeaker and the internal microphone and storing the transfer function into a second filter, providing a preferred related function reflecting correlations between the transfer functions and storing the preferred related function in a control unit which connected between the external microphone and the internal loudspeaker, removing the internal microphone disposed in the ear cup of the noise reduction headset, and obtaining the noise reduction headset. The step for providing the preferred related function includes:
inputting external noise sound signals respectively through the first filter and the second filter so as to obtain target signals by the first transfer function and raw signals by the second transfer function;
inputting the raw signals from the second filter into a controller so as to obtain output signals, wherein the output signals are obtained by the raw signals processed by a related function stored in the controller, the related function being obtained from adaptive control methods;
inputting the output signals from the controller and the target signals into a comparator so that the output signals from the controller are compared with the target signals in the comparator; and
regulating the related function until the comparison between the output signals and the target signals reaches a minimum value to thereby obtain the preferred related function from the related function.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which:
The present invention provides a noise reduction headset and a method for providing the noise reduction headset. Referring to
Referring to
Reference will now be made to show a method for obtaining the transfer function from the external microphone 22 to the internal microphone 24 in detail. The noise generator 26 of the frequency analyzer 25 generates white noise sound signals which are sent to the sound source 27, from which the white noise sound signals are broadcasted. The white noise sound signals, in one aspect, are received by the external microphone 22. The white noise sound signals, in another aspect, transfer through the ear cup 21 and are received by the internal microphone 24. The white noise sound signals are weakened by the ear cup 21 when they transfer therethrough. The white noise sound signals received by the external and internal microphones 22, 24 are respectively sent to the frequency analyzer 25. The frequency analyzer 25 analyzes the received white noise sound signals and obtains the transfer function between the external microphone 22 and the internal microphone 24. In this embodiment, there is a linear amplifier 28 connected between the external microphone 22 and the frequency analyzer 25. The linear amplifier 28 amplifies the white noise sound signals sent from the external microphone 22 so as to facilitate the frequency analyzer 25 to receive and process the white noise sound signals from the external microphone 22. Alternatively, if the white noise sound signals from the external microphone 22 are so powerful that the frequency analyzer 25 can process them directly, there is no need to arrange the linear amplifier 28.
Reference will now be made to show a method for obtaining the transfer function from the internal loudspeaker 23 to the internal microphone 24 in detail. The noise generator 26 of the frequency analyzer 25 generates, in addition to the white noise sound signals, also pink noise sound signals. The white noise sound signals are broadcasted by the internal loudspeaker 23, during which the output characteristic curve of the internal loudspeaker 23 in the gamut can be obtained. The white noise sound signals broadcasted by the internal loudspeaker 23 is received by the internal microphone 24 in the ear cup 21 during which the response characteristic curve of the internal microphone 24 in the gamut can be obtained. The white noise sound signals received by the internal microphone 24 are transmitted to the frequency analyzer 25. The pink noise sound signals are also broadcasted by the internal loudspeaker 23, received by the internal microphone 24 and finally transmitted to the frequency analyzer 25. The frequency analyzer 25 analyzes the received white and pink noise sound signals and thereby obtains the transfer function between the internal loudspeaker 23 and the internal microphone 24.
Reference will now be made to show a system for providing a preferred related function reflecting correlations between the transfer function from the external microphone 22 to the internal microphone 24 and the transfer function from the internal loudspeaker 23 to the internal microphone 24 in detail. Referring to
Referring to
In the present noise reduction headset 40, each headphone 49 merely includes one microphone i.e. the external microphone 42. This makes the simplified noise reduction headset 40 occupy a compact size and further has a lower cost than the related noise reduction headset 10 of
It is to be understood, how ever, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
---|---|---|---|
200710123708.6 | Sep 2007 | CN | national |