GB2498812A

GB2498812A - Providing an time delayed and pitched shifted accompaniment to a sound produced by a user

Info

Publication number: GB2498812A
Application number: GB1201565.7A
Authority: GB
Inventors: David Keating; James Watt; Harry Thomson
Original assignee: China Industries Ltd
Current assignee: China Industries Ltd
Priority date: 2012-01-30
Filing date: 2012-01-30
Publication date: 2013-07-31
Also published as: GB201201565D0

Abstract

A method and apparatus for providing an accompaniment to a sound produced by a user is described. The method comprises generating an electrical output signal from a sound produced by a user, preferably using a microphone 2. A time delay and a shift in the pitch is introduced to the electrical output signal before an audio output is generated. The time delay may be variable, in the range of 38 ms to 140 ms, and may reduce with an increase in amplitude of the electrical output signal. The pitch shift may involve shifting the pitch up an octave, by identifying the fundamental frequency or cycle time of the electrical output signal and transmitting a sample of the cycle time at twice the sample rate. The described method can be incorporated within a novelty soft toy 1, such as a doll or animal, so that it appears to sing a highly realistic duet with the user. An audio speaker may be incorporated into the soft toy 1.

Description

1 Musical Toy 3 The present invention relates to the field of musical toys. In particular, a musical toy which 4 provides an accompaniment for a sound produced by a user is described. The described musical toy finds particular application as a singing accompaniment for the user.

7 Background to the Invention

9 A number of musical toys are known in the art which provide a singing accompaniment means for a user. For example, there exist a number of toy microphones which are 11 designed to play music while providing sound amplification for sound input provided by the 12 user. These toy microphones may alternatively be incorporated as part of a keyboard 13 system wherein the user can sing along as they play or with pre-programmed music stored 14 within the keyboard memory.

16 Alternatively, there exist a number of musical toys which take the form of interactive 17 entertainment or video games in which singers sing along with recorded music (a music 18 video) using a microphone and public address system, so called karaoke" systems. The 19 music is typically a well-known pop song minus the lead vocal. Lyrics are usually 1 displayed on a video screen, along with a moving symbol, that changes colour, or music 2 video images, to guide the singer though the song.

4 It is therefore an object of an embodiment of the present invention to provide an alternative musical toy that provides a novel means for accompanying sound produced by a user e.g. 6 when singing.

8 Summary of the Invention

According to a first aspect of the present invention there is provided a method for providing 11 an accompaniment to a sound produced by a user wherein the method comprises 12 -generating an electrical output signal in response to the sound produced by a user; 13 -introducing a time delay to the electrical output signal; 14 -shifting the pitch of the electrical output signal; and -generating an audio output from the electrical output signal.

17 The above method provides a system which provides a realistic accompaniment to the 18 sound produced by a user. This is achieved through the combination of the induced delay 19 and shifting of the pitch of the electrical signal. The methodology finds particular application within a musical toy, when the sound produced by a user is in the form of 21 singing, since the audio output comprises a realistic accompaniment that appears to be 22 singing a duet with the user.

24 The time delay introduced to the electrical output signal may comprise a variable time delay. Having a variable time delay increases the realism of the accompaniment to the 26 sound produced by the user.

28 Preferably the time delay varies dependent upon the amplitude of the electrical output 29 signal.

31 Optionally the time delay reduces in response to an increase in the amplitude of the 32 electrical output signal.

34 The time delay may be in the range of 38 ms to 140 ms.

1 Most preferably the shifting of the pitch of the electrical output signal comprises shifting the 2 pitch up an octave.

4 The shifting of the pitch of the electrical output signal up an octave may comprise indentifying the fundamental frequency or cycle time of the electrical output signal.

7 The shifting of the pitch of the electrical output signal up an octave may further comprise: 8 -sampling the electrical output signal for a single cycle time of the electrical output 9 signal; -transmitting the sampled single cycle of the electrical output signal for a first time at 11 twice a sample rate of the saved single cycle; and 12 -transmitting the sampled single cycle of the electrical output signal for a second 13 time at twice the sample rate of the saved single cycle.

Most preferably the shifting of the pitch of the electrical output signal pitch up an octave 16 further comprises repeating steps the above steps.

18 Preferably the identification of the fundamental frequency or cycle time of the electrical 19 output signal comprises analysing a short sample length of the electrical output signal so as to identify two or more zero-crossing points. The time between two zero-crossing 21 points is then set to be the fundamental frequency or cycle time of the electrical output 22 signal. This provides a very simple method for identifying the fundamental frequency 23 which does not require a high level of processing power but which is of sufficient accuracy 24 for use in a musical toy.

26 The first and second cycles of the transmitted sampled single cycle are preferably 27 transmitted such that they are joined at their zero-crossing points. This has the advantage 28 that glitches or anomalies at the cycle length rate are avoided thus improving the overall 29 quality of the first electrical output signal.

31 According to a second aspect of the present invention there is provided a musical toy 32 suitable for providing an accompaniment to a sound produced by a user wherein the 33 musical toy comprises a microphone that provides a moans for generating an electrical 34 output signal for one or more audio speakers, a signal delay chip configured to introduce a 1 time delay to the electrical output signal and a microprocessor configured to shift the pitch 2 of the electrical output signal.

4 Preferably the musical toy further comprises a low pass filter located between the microphone and the signal delay chip.

7 It is preferable for the musical toy to further comprise a DC bias circuit located between the 8 microphone and the signal delay chip.

Most preferably the audio speaker is incorporated within a soft toy. The soft toy may 11 comprise a doll, an animal or an alien.

13 Embodiments of the second aspect of the invention may include one or more features of 14 the first aspects of the invention or its embodiments, or vice versa.

16 Brief description of the drawings

18 There will now be described, by way of example only, various embodiments of the 19 invention with reference to the drawings, of which: 21 Figure 1 illustrates in schematic representation of a musical toy in accordance with an 22 embodiment of the present invention; 24 Figure 2 illustrates a schematic diagram of the electrical circuit employed by the musical toyofFigurel; 27 Figure 3 provides an illustration of a delay introduced to an input signal to a signal delay 28 chip of the electrical circuit Figure 2; Figure 4 presents a flow chart of the methodology employed by a microprocessor of the 31 electrical circuit of Figure 2; and 33 Figure 5 presents a flow chart of the methodology employed by the musical toy of Figure 34 1.

1 Detailed Description

3 With reference to Figure 1, there is presented a schematic representation of a musical toy, 4 as depicted generally by reference numeral 1. The musical toy 1 can be seen to comprise a microphone 2 which is hardwired to a toy cat 3. It will be appreciated by the skilled 6 reader that the microphone 2 may be wirelessly connected to the toy cat 3 and/or that the 7 toy cat 3 may lake a number of alternative forms e.g. other animals, human or alien forms 8 etc. Figure 2 illustrates a schematic diagram of an electrical circuit employed by the musical 11 toy 1, as depicted generally by reference numeral 4. The electrical circuit 4 can seen to 12 comprise a signal delay chip 5 (a Holtek® HT8970 being an example of such a chip 5).

13 The Holtek® HT8970 signal delay chip 5 is an off the shelf echo/surround effect processor.

14 It comprises a built in preamplifier, VCO or Voltage Control OSC, 20Kb SPAM, AID and D/A convertors as well as delay time control logic. The function of the signal delay chip 5 16 is described in further detail below.

18 The signal delay chip 5 is arranged to receive and process the electrical output signal 6 19 generated by the microphone 2 before relaying this signal 6 on to a microcontroller 7 (a Microchip® Pic 18F2455 being an example of such a microcontroller 7). Further 21 processing of the output signal 6 takes place within the microcontroller 7 before it is 22 relayed to an audio speaker S (a Visatron® K5O) being an example of such a speaker 8).

24 It will be appreciated by the skilled reader that more than one speaker could alternatively be employed to generate independent audio outputs from the output signal 6.

27 As can be seen from Figure 2, before reaching the signal delay chip 5 the electrical output 28 signal 6 can be seen to pass through a low pass frequency filter 9 so as to remove 29 frequency components above 3KHz and reducing the detrimental effects of aliasing of the sampled signals within the signal delay chip 5. The output of the low pass frequency filter 31 9 is then provided as an input to pins 15, 16 and 6 of the signal delay chip 5. Before 32 reaching pin 6 the electrical output signal 6 is passed through a first 10 and a second 11 33 transistor circuit which combine to vary the resistance to pin 6 depending on the amplitude 34 of the output signal 6. In the presently described embodiment, the resistance to pin 6 ranges from 22 kO when the amplitude of the output signal 6 is zero (i.e. detecting 1 background noise only), down to a minimum of 3.9 kO when the microphone 2 is detecting 2 sound produced by the user.

4 A DC bias circuit 12 is also provided between the microphone 2 and the signal delay chip 5, the output of which is relayed to pins 2, 3 and 4 of the signal delay chip 5. The function 6 of the DC bias circuit 12 is to provide a bias voltage to the electrical output signal 6 so as 7 to match the DC bias point of this signal 6 to that of the signal delay chip 5. This is useful 8 because the signal delay chip 5 has only a ground (zero volts) and a positive supply 9 voltage (+SV supply as can be seen to be provided to pin 1 of the signal delay chip 5), and so the DC bias circuit 12 allows for biasing of the electronics at a point between zero and 11 this positive supply. Preferably the bias point is set to half the positive supply voltage 12 therefore allowing equal positive and negative signals about this bias point.

14 In the configuration presented in Figure 2 the signal delay chip 5 acts to introduce a variable delay to the output signal 6 that is dependent upon the amplitude of the output 16 signal 6. As can be seen from Figure 3, a delay of 140 ms is introduced to the output 17 signal 6awhen there is no sound (or background sound only) detected by the microphone 18 2. However, when the microphone 2 detects sound produced by the user the induced 19 delay decays towards 38 ms with an exponential delay time of 0.5 seconds. When sound is no longer detected by the microphone 2 the reverse process takes place and the 21 induced delay increases back towards 140 ms with a logarithmic delay time of 0.5 22 seconds. The significance of the amplitude dependent delay upon the output signal 6 will 23 be described in further detail below.

The function of the microcontroller 7 is to shift the pitch of the output signal 6 relayed to it 26 by the signal delay chip 5. In the presently described embodiment the pitch of the output 27 signal 6 is shifted up an octave. This is achieved by programming the microcontroller so 28 as to process the output signal 6 as presented schematically within the flow chart of Figure 29 4.

31 The first step is to employ the microcontroller 7 so as to indentify the fundamental 32 frequency or cycle time of the output signal 6. The microcontroller 7 is thereafter 33 employed to: 34 -Sample a single cycle of the output signal 6; 1 -Transmit the sampled single cycle of the output signal 6 for a first time at twice the 2 sample rate of the sampled single cycle; and 3 -Transmit the sampled single cycle of the output signal 6a for a second time at twice 4 the sample rate of the sampled single cycle.

6 The microcontroller 7 then continues by repeating the above described process steps.

8 The identification of the fundamental frequency or cycle time of the output signal 6 is 9 achieved by saving a short sample length of the output signal 6 in the temporary memory of the of the microcontroller 7 and thereafter analysing the sample length so as to identify 11 the zero-crossing points. Typically, sample length of the output signal 6 is in the range of 12 1 ms to 4ms e.g. 1.Sms. The time between the first two zero-crossing points is then set to 13 be the fundamental frequency or cycle time of the output signal 6. This provides a very 14 simple method for identifying the fundamental frequency which does not require a high level of processing power but which is of sufficient accuracy for use in a musical toy.

17 The sampling of the single cycle of the output signal 6 is preferably performed within the 18 temporary memory of the microcontroller 7. It is preferable for the memory of the 19 microcontroller 7 to be configured so as to comprise a first and a second buffer and that sampling of sequential single cycles of the output signal 6 is toggled between the first and 21 second buffers. . In this way one of the buffers provides the means for transmitting a 22 single cycle of the output signal 6a while the other buffer is employed to sample the next 23 single cycle of the output signal 6. As a result, only a small temporary memory is required 24 within the microcontroller 7 so as to allow for the pitch of the output signal 6 to be varied.

26 The two cycles of the transmitted sampled single cycle are preferably transmitted such that 27 they are joined at their zero-crossing points. This has the advantage that glitches or 28 anomalies at the cycle length rate are avoided thus improving the overall quality of the 29 output signal 6 transmitted at the higher pitch.

31 The overall methodology of the musical toy will now be described with reference to the 32 flow chart of Figure 5: 33 -In the first instance the microphone 2 is employed to generate an electrical output 34 signal 6 that is relayed to the signal delay chip 5; 1 -The electrical output signal 6 is processed by the signal delay chip 5 so as to 2 introduce a delay upon the output signal 6 that is dependent upon its amplitude.

3 Preferably the delay introduces upon the output signal 6 is variably dependent 4 upon its amplitude; -The delayed output signal is then relayed to the microcontroller 7 which acts to shift 6 the pitch of the delayed output signal 6; 7 -The delayed and shifted output signal 6 is then relayed to the speaker 8 so as to 8 provide an audio output.

The overall effect of the electrical circuit 4 is to provide the user with an accompanying 11 sound that raised one octave higher in pitch. The variable delay makes it sound as though 12 the accompaniment is at first out of time with the direct user's sound but which quickly 13 becomes synchronised. Leaving a residual delay (in the above described embodiment of 14 38 ms) between the direct user sound and the accompanying sound maintains a realistic nature to the accompaniment or the mimicking of the users voice by the toy cat 3. Of 16 particular interest is when a user sings into the microphone 2. At this time the toy cat 3 17 appears to sing a realistic duet with the user.

19 It will be appreciated by the skilled reader that a number of alternative features may be introduce to the musical toy so as to increase the playing experience. For example, the 21 musical toy may be configured to play music itself which the user is encouraged to sing 22 along with.

24 In addition if a user collects more than one toy, a choir can be formed, with each individual toy producing an output in their character, and appearing to sing along to the user's voice.

26 This effect would be enhanced if the minimum delay introduced by the signal delay chip 27 varied between each musical toy.

29 In further alternative embodiments other effects may be introduced to the audio output generated by the output signal 6 so as to further characterise the accompaniment to the 31 sound produced by a user. In yet further alternative embodiments non-voice sounds 32 effects may be stored and emitted by the device as triggered by different notes of the 33 original voice of the user, so as it appears for example that a dog, other animal or fictional 34 alien is singing along with the user.

1 The presently described embodiments offer a number of advantages over those musical 2 toys known in the art. The described device provides a novelty toy, such as a doll or 3 animal, that appears to sing a duet with its user. The pitch shifting technique is achieved 4 through the use of a simple microprocessor and so does not require the high levels of processing powers associated with prior art techniques based of Fast Fourier Transforms 6 or Wavelet analysis. Furthermore the described time delay techniques are also achieved 7 through the employment of cheap, off the shelf electrical components. This makes the 8 electrical circuit cost effective and therefore commercially viable for use within a musical 9 toy.

11 A method and apparatus for providing an accompaniment to a sound produced by a user 12 is described. The method initially comprises generating a an electrical output signal from a 13 microphone. A time delay and a shift in the pitch is then introduced to the electrical output 14 signal before an audio output is generated from the electrical output signal. The described method can be incorporated within a novelty toy, such as a doll or animal, so that it 16 appears to sing a highly realistic duet with the user.

18 The foregoing description of the invention has been presented for the purposes of 19 illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in 21 order to best explain the principles of the invention and its practical application to thereby 22 enable others skilled in the art to best utilise the invention in various embodiments and 23 with various modifications as are suited to the particular use contemplated. Therefore, 24 further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.