GB2335296A

GB2335296A - Computer interface apparatus

Info

Publication number: GB2335296A
Application number: GB9905502A
Authority: GB
Inventors: Danny Boyle
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-03-12
Filing date: 1999-03-11
Publication date: 1999-09-15
Also published as: GB9905502D0; GB9805175D0

Abstract

An audio interface device for connecting an analogue audio output 24 of a digital sound recording device to an analogue microphone input 26 of a computer has resistance means connected between the audio output and microphone input. The value of the resistance means is such that any degradation of an audio signal input to the microphone input is eliminated or reduced to an extent which enables voice recognition software installed on the computer to operate to a level of performance comparable to that obtained with direct speech input via a microphone.

Description

1 1 Computer Interface AMaratus 2 3 4 6 7 8 9 10 11 12 13 14 is 16 17 18

19 20 21 22 23 24 25 2335296 The present invention relates to a device for facilitating the use of audio inputs and outputs of personal computers (PCs). The invention is particularly, but not exclusively, concerned with an interface enabling recorded speech signals to be input to a computer to enable voice recognition to be performed on the input speech signals.

Voice recognition software has been available for desktop PC use for approximately five years. Voice recognition software enables audio speech signals to be converted directly into digitally encoded text. Software of this type has only recently reached a level of maturity to enable reliable recognition of continuous speech. All such software is designed to speech signals input directly to the a microphone connected to a standard microphone socket on the motherboard or soundcard of the PC. This limits the use which can be made of the software since the user requires access at least to a portable (laptop) computer to enable the speech to be input to the system.

operate on "live" PC by the user via 2 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 It would clearly be desirable for voice recognition systems to operate on pre-recorded audio signals which could be recorded on any suitable recording unit and subsequently downloaded to the computer. It would also be desirable for commonly available, compact, portable recording devices to be usable for recording purposes.

It is also desirable that the recording device should be capable of being connected to the computer in a manner which is as simple as possible.

At the present time, no systems are available which allow a standard recording device to be easily connected to a computer in such a way that pre-recorded speech signals can be input to the computer in a manner which allows voice recognition to be performed on the signals in an acceptable manner.

In the course of investigating the possibility of downloading prerecorded speech to a computer for voice recognition purposes, the present inventor has arrived at the following conclusions:

(a) Commonly available analogue recording devices do not produce an output signal of sufficient fidelity to be usable with commercially available voice recognition systems. Accordingly, it is necessary to use a high fidelity digital recording device.

(b) For reasons of simplicity and convenience, it would be desirable to connect the recording device to the computer via the standard analogue audio output socket of the recorder (typically a headphone socket) and the standard microphone input socket of the computer. However, it has 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 been found that connecting the respective sockets simply by means of a length of cable and suitable jack plugs results in signal degradation which renders the signal received by the computer unusable for reliable voice recognition.

(c) Many users of multimedia PC equipment have difficulty in identifying the correct sockets to which items such as headphones, loudspeakers and microphones should be connected.

In accordance with a first aspect of the invention, there is provided audio interface device for connecting an analogue audio output of a digital sound recording device to an analogue microphone input of a computer, said apparatus comprising a first connector for connection to said audio output, a second connector for connection to said microphone input, and resistance means connected between said first and second connectors, the value of said resistance means being selected such that any degradation of an audio signal input to said microphone input is eliminated or reduced to an extent which enables voice recognition software installed on said computer to operate on said audio signal to a level of performance comparable to that obtained with direct speech input via a microphone.

Surprisingly, it has been found that the use of simple resistance elements in the signal path between the recording device and the microphone input provides a signal of sufficient fidelity to enable voice recognition software to operate reliably on the recorded speech.

For standard 3.5 mm stereo jack type audio outputs and microphone inputs, it has been found that a series 4 1 2 3 4 5 6 7 8 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 31 32 33 34 35 36 resistance of 44 kQ provides excellent results. This specific resistance is selected at least partially on the basis of commonly available resistors. being easily implemented using two series-connected 22 kO resistors.

Preferably, the interface is adapted to combine left and right audio channels from a stereo audio output and to apply the combined signal to the resistance means, and subsequently to divide the combined signal into left and right audio components for connection to a stereo microphone input.

In accordance with a second aspect of the invention, there is provided an audio interface unit for use with a multimedia computer, said unit including at least two audio output sockets, at least one microphone input and at least one interface device in accordance with the first aspect of the invention, a microphone output connector for connection to a microphone input of a computer and a loudspeaker input connector for connection to a loudspeaker output socket of a computer, first switch means whereby said microphone output may be connected selectively to either said at least one microphone input or to said interface device, and second switch means whereby said loudspeaker input may be selectively connected to either one of said at least two audio output sockets.

It will be understood that the interface device includes said first connector for connection to an audio source, as defined in relation to the first aspect of the invention, and that the microphone output connector of the second aspect of the invention comprises the second connector of the first aspect when the first switch means is operated to connect the microphone output of the interface unit to the 1 1 2 3 4 5 6 7 8 9 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 interface device.

The unit preferably comprises a housing with said first and second audio outputs, the microphone input and said first and second switch means located on the exterior surface thereof, and wherein the first connector of the interface device, the microphone output connector and the loudspeaker input connector are provided at the end of trailing cables extending from the housing.

The various connectors preferably comprise 3.5 mm jack plugs and sockets, most preferably stereo plugs and sockets.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic plan view of an audio interface unit in accordance with the second aspect of the invention, incorporating an interface device in accordance with the first aspect of the invention; Figs. 2 and 3 are first and second side elevations of the unit of Fig. 1; and Fig. 4 is a circuit diagram of an interface device in accordance with the first aspect of the invention.

Referring firstly to Figs. 1 to 3, an audio interface unit comprises a housing 10 having various audio inputs and outputs as follow:

first input socket 12 for receiving a jack plug 14 of a microphone (not shown); first output socket 16 for receiving a jack plug 18 of a loudspeaker or, more usually, a pair of stereo 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 loudspeakers (not shown); a second output socket 20 for receiving a jack plug 22 of a set of headphones (not shown); a first input jack plug 24, connected to the unit by a first cable 25, for connection to an audio output of a source (not shown) of a pre-recorded audio signal; a first output jack plug 26, connected to the unit by a second cable 28, for connection to a microphone input socket of a computer (not shown); and a second input jack plug 30, connected to the unit by a third cable 32, for connection to a loudspeaker output socket of a computer (not shown).

The first input jack plug 24 is connected via the first cable 25 to a printed circuit board (PCB) 34 within the housing 10. The PCB 34 includes the circuitry of an interface device in accordance with the first aspect of the invention, described in greater detail below.

The unit further includes a first switch 36 and a second switch 38, whereby the various audio outputs may be selectively connected to the various audio outputs, as follows: when the first switch 36 is in a first position, A, the first output jack plug 26 is connected to the microphone socket 12, enabling speech or other,live,, audio signals to be input to the computer via a microphone connected to the socket 12; when the first switch 36 is in a second position, B, the first output jack plug 26 is connected, via the interface device on the PCB 34, to the first input jack plug 24, enabling pre-recorded audio signals to be input to the computer from a source connected to the jack plug 26; when the second switch 38 is in a first position, A, the second input jack plug 30 is connected to the 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 first output socket 12, enabling audio ' output from the computer to be heard via loudspeakers connected to the socket 12; when the second switch 38 is in a second position, B, the second input jack plug 30 is connected to the second output socket 20, enabling audio output from the computer to be heard via headphones connected to the socket 16.

The unit facilitates the use of various audio input and output devices with a computer. The jack plugs 26 and 30 can be connected to the microphone and loudspeaker sockets of the computer, with the cables 28 and 32 allowing the unit to be located at any convenient position on or around the user's desktop. A microphone, loudspeakers, headphones and an audio source can all be connected to the unit at the same time, via the sockets 12, 16 and 20 and the jack plug 24. The user may then select the required audio input and output devices (microphone or audio source, and loudspeakers or headphones) simply by operation of the switches 36 and 38, without any need for swapping connections either to the interface unit or to the computer itself.

The interface device in accordance with the first aspect of the invention enables an audio source to be connected to the microphone input of the computer, in a manner which enables voice recognition software to operate reliably on pre-recorded speech (dependent, of course, on the quality of the recorded signal being of sufficient fidelity in the first place).

As illustrated in Fig. 4, the interface device in accordance with the first aspect of the invention comprises a series resistance R1, R2, connected in the 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 signal path between the output from the audio source and the microphone input of the computer. The interface includes a first connector (jack plug) for connection to the audio output of the audio source and a second connector (jack plug) for connection to the microphone input socket of the computer. In the context of the interface unit of Figs. 1 to 3, the first connector comprises the jack plug 24 and the second connector comprises the jack plug 26 (when the first switch 36 is in its second position, B). It will be understood that the interface device could be implemented independently of the interface unit, by including the necessary resistance in a simple cable having a jack plug at either end, or in some other form.

It has been found that the inclusion of a simple resistance of an appropriate value in the signal path allows the signal from the audio source to be input to the microphone socket of a computer without any significant degradation of signal quality, as has been found to occur if the source output is simply connected directly to the microphone input. For standard 3.5 mm jack-type audio outputs and microphone inputs, good results are obtained using a total resistance of 44 kQ, comprising two series connected 22 kO resistors (preferably, +/- 5%, 0.25 W components are used) This is believed to be an optimal or near optimal value using readily available resistors, for standard jack type outputs and inputs. Acceptable results can be expected to be obtained with a resistance value which varies from this preferred value. The upper and lower limits for the resistance value which produces acceptable results can be determined empirically.

In order to ensure that the source signal is of 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 adequate quality, it is preferred that the source signal is recorded using a digital recording medium (although the output will be an analogue signal). The recorded signal need not be played back from the same device used to record the signal. Since the invention will typically be used for the purposes of transcribing pre-recorded dictation, it is preferred that the recording device is a purpose-made dictation machine. It is particularly preferred that the interface device is employed in combination with a digital dictation machine of the type in which the recording is stored in solid state memory, in which case it is most likely that the signal will be played back from the same machine on which it was recorded, rather than being transferred to a separate machine for play back, as would be more likely with tape- or disc-based recorders.

Assuming that the output from the audio source is a stereo output and that the microphone input is also of the stereo type, it is preferred that the left and right audio channels from the source are combined 1upstream11 of the resistors R1, R2 and the resultant monophonic signal subsequently divided into left and right components "downstream" of the resistors, as illustrated. This arrangement could be varied as required to suit different combinations of stereo and mono outputs and inputs. However, the arrangement illustrated, using stereo jack plugs, will suit all combinations, assuming that there is no need for a genuine stereo signal to be input to the computer (which is unlikely for voice recognition purposes) The various aspects of the invention have a number of advantages, as follow: facilitates the use of voice recognition software 1 in a mobile dictation environment; 2 eliminates the requirement for end-users to 3 interchange cable connections to the PC; 4 Facilitates the switching of input and output devices; 6 Automatically attenuates signal and line levels.

7 8 Improvements and modifications may be incorporated 9 without departing from the scope of the invention.

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Claims

1. An audio interface device for connecting an analogue audio output of a digital sound recording device to an analogue microphone input of a computer, said apparatus comprising a first connector for connection to said audio output, a second connector for connection to said microphone input, and resistance means connected between said first and second connectors, the value of said resistance means being selected such that any degradation of an audio signal input to said microphone input is eliminated or reduced to an extent which enables voice recognition software installed on said computer to operate on said audio signal to a level of performance comparable to that obtained with direct speech input via a microphone.

2. A device as claimed in Claim 1, for use with standard 3.5 mm stereo jack type audio outputs and microphone inputs, wherein said resistance means provides a resistance of about 44 kg.

3. A device as claimed in Claim 1 or Claim 2, adapted to combine left and right audio channels from a stereo audio output and to apply the combined signal to the resistance means, and subsequently to divide the combined signal into left and right audio components for connection to a stereo microphone input.

4. An audio interface unit for use with a multimedia computer, said unit including at least two audio output sockets, at least one microphone input and at least one interface device in accordance with the first aspect of the invention, a microphone output connector for connection to a microphone input of a computer and a loudspeaker input connector for connection to a 12 1 2 3 4 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 loudspeaker output socket of a computer, first switch means whereby said microphone output may be connected selectively to either said at least one microphone input or to said interface device, and second switch means whereby said loudspeaker input may be selectively connected to either one of said at least two audio output sockets.

5. A device as claimed in Claim 4, comprising a housing with said first and second audio outputs, the microphone input and said first and second switch means located on the exterior surface thereof, and wherein the first connector of the interface device, the microphone output connector and the loudspeaker input connector are provided at the end of trailing cables extending from the housing.

6. A device as claimed in Claim 4 or Claim 5, wherein the various connectors comprise 3.5 mm jack plugs and sockets.

7. An audio interface device for connecting an analogue audio output of a digital sound recording device to an analogue microphone input of a computer, substantially as hereinbefore described with reference to the accompanying drawings.

8. An audio interface unit for use with a multimedia computer substantially, as hereinbefore described with reference to the accompanying drawings.