GB2103375A - Display apparatus - Google Patents

Abstract

An input sound signal from a source (1) is displayed visually using a plurality of arrays of light sources (8), preferably arranged in rows and columns. Signals representing the frequency content of the sound input are obtained at successive times and each signal is supplied in turn to the arrays of light sources, so that the arrays, when energised, show the current frequency content on one row and the frequency content at at least one earlier time on another row. The input signal is clipped (4) and the frequency is determined indirectly (in 6) by measurement of the time intervals between successive crossings of a datum line by the clipped signal. Accumulator devices (12) are associated with each column and the accumulated signals are shifted at inter <IMAGE>

Description

SPECIFICATION Display apparatus The invention relates to the display of electric signals representative of a sound input.

Sound waveforms can be displayed visually on an oscilloscope, or the sound energy content of discrete frequency bands, average over a time period, can be displayed by means of a sound spectrometer. These techniques find application in research and in teaching deaf persons; the apparatus is necessarily complicated and expensive if a display is to be held for any length of time without loss of incoming information.

The invention accordingly consists in a method of and an apparatus for providing a display dependent on a sound input, in which signals representing the frequency content of the sound input are obtained at successive times and each signal is supplied in turn to at least two arrays of output transducers, so that the arrays at any time show respectively the current frequency content and the frequency contents at at least one earlier time.

Conveniently, each array comprises a row of light sources associated with respective adjacent frequency bands, of which for example sixteen may be provided for within a range of for example approximately 30 Hz to 20 kHz, or conveniently 300 Hz to 3 kHz. The rows of light sources, of which for example eight in all may be provided, can be arranged in parallel formation to provide a rectangular matrix of light sources. The output transducers need not be light sources but could for example comprise electrodes for passing currents to the skin of an observer.

The electric inputs to the transducers can be obtained in any suitable way, as by filtering a sound-generated electric signal in "sub-octave" filters, but such filters are complex and expensive.

The invention therefore also provides a method of and an apparatus for analysing the frequency content of an electric signal, such as a sound dependent signal, in which the signal is first clipped and the frequency then determined indirectly by measurement of the time interval between successive crossings by the clipped signal of zero or other datum line. The presence of successive crossings within a predetermined time range indicates the presence of a frequency within an associated frequency range, and the apparatus is arranged to provide an output on an associated output line when the presence of a frequency within the range is detected during a predetermined measurement period.

Thus the present apparatus, for use with the visual display apparatus described above, can be provided with for example sixteen output lines each extending to a respective one of the light sources of the first row.

The signals appearing on these lines during a measurement period are stored and transferred to the next adjacent row at the end of the period to make place for signals appearing during the next measurement period, each set of signals being thus transferred successively from the first to the last row provided. The clipping step removes amplitude information from the signal but the apparatus when used in this manner is intended to display not the amplitude of the individual frequency ranges but whether or not an individual frequency range is present during a measurement period.

The visual display of information, not not only about the sound spectrum during an immediately preceding measurement period, but about the spectrum during as many earlier periods as there are additional rows of light sources provided, assists recognition of sound patterns by persons not of normal hearing. The invention can be embodied in apparatus for entertainment purposes also, for example, with coloured light sources responsive to sound produced by musicians.

The invention is further described below by way of example with reference to the accompanying drawings, in which: Figure 1 schematically shows a visual sound display apparatus including a display device comprising an array of lamps and an associated sound signal analysis device, shown in block diagram form; and Figure 2 shows the general appearance of the display device.

The illustrated sound display apparatus comprises a source 1 of a sound-responsive electric signal. The source can conveniently comprise a microphone positioned to receive the sound to be displayed, but the signal could be otherwise obtained, as from a tape head reading a tape on which the signal had been previously recorded.

The signal from the source 1 is supplied to a signal analysis device comprising an amplitude and tone control device 2 at which the contribution to the signal of various frequency bands within it may be selectively adjusted. The signal is then clipped in a clipper device 4 so that only the dominant frequency is present at any instant. The signal frequency is then determined indirectly, by measurement of the time interval between successive crossings of zero by the clipped waveform, in a time interval measurement device 6.

The display device of the apparatus comprises a rectangular bank of one-hundred and twenty-eight lamps 8 arranged in sixteen columns and eight rows. The lamps are conveniently located in a common plane which may be vertical so as to be easily read. From right to left, the columns are designated COL. PI, COL. 1... COL.

15, and the rows are designed ROW 0, ROW 1... ROW 8from bottom to top. Each lamp 8 can be energized by way of a respective register 10 and the registers of each column are connected in series with one another and with a respective accumulator device 12. The time interval measurement device 6 has sixteen output lines each extending to one of the accumulator devices 12. A control unit 14 is arranged to supply "clear" pulses on line 15 to the accumulator devices 12 and "shift" pulses on line 16 to the accumulator devices and to the registers 10 at predetermined intervals.

In operation, the measurement device 6 provides an output on the appropriate one of the output lines, to increment the accumulator device to which the line is connected, whenever a time interval between zero crossings of the clipped waveform appropriate to that accumulator device is detected. The frequency bands allocated to the accumulator device 12 of the various columns can be in accordance with the following table which show also the equivalent time range.

Frequency Range Equivalent Time Column (Hz) Range (milliseconds) 3000 > f 3 2600 0.333 < t S 0.385 1 2600 > f 3 2250 0.385 < t S 0.445 2 2250 > f 3 1948 0.445 < t S 0.513 3 1948 > f 3 1687 0.513 < t S 0.593 4 1687 > f 3 1461 0.593 < t < 0.685 5 1461 > f 3 1265 0.685 < t S 0.791 6 1265 > f 3 1096 0.791 < t S 0.913 7 1096 > f 3 949 0.913 < t S 1.054 8 949 > f 3 822 1.054 < t S 1.217 9 822 > f 3 711 1.217 < t < 1.406 10 711 > f 3 616 1.406 < t S 1.623 11 616 > f 3 534 1.623 < t S 1.874 12 534 > f 3 462 1.874 < t S 2.165 13 462 > f 3 400 2.165 < t S 2.500 14 400 > f 3 346 2.500 < t S 2.887 15 346 > f 3 300 2.887 < t S 3.333 At the end of each measurement period, the control unit 14 supplies a shift pulse on line 15so that the contents of each register 10 are shifted into the register of the adjacent higher numbered row, and the contents of each accumulator device 12 are transferred to the associated register 10 of ROW p. To being the next measurement period, a clearing pulse on time 16 empties the accumulator devices. The accumulator devices 12 can have four states, for example, corresponding respectively to "lamp off", "lamp dim", "lamp at half brightness" and "lamp at full brightness". A suitable measurement period is 67 milliseconds, so the display is updated about 15 times per second.

It will be evident that the embodiment described can be modified in many ways. The number and width of the frequency bands can otherwise be selected as can the number of rows; a useful apparatus could comprise as few as eight columns and three rows, and the accumulator device could be a two state device, providing only "lamp on" and "lamp off" conditions. The rectangular arrangement of the lamps can be varied, particularly for entertainment purposes, for example so that the columns extend radially from a centre, or the rows transposed one with another. The signal analysis device could be constituted by a microprocessor.

Claims (23)

1. A method of converting sound information into a form to be appreciated by the visual and/or tactile senses, which comprises producing a sequence of signals representative of the frequency content of an input sound signal at successive time instants or during successive time periods, and feeding said signals in turn to at least two arrays of output transducers so that at any time when said transducers are energised one array represents the frequency content at one time instant or in one time period and the other or another array represents the frequency content at at least one earlier time instant or in at least one earlier time period.

2. A method as claimed in claim 1, in which each array comprises a plurality of light sources each associated with respective adjacent frequency bands.

3. A method as claimed in claim 1, in which each array comprises a plurality of electrodes to be attached to the skin and each associatedwith respective adjacent frequency bands.

4. A method as claimed in claim 1,2 or 3, which includes transferring the composite signals representative of frequency content, within a series of arrays, from each array to the next array at the end of predetermined measurement periods, thereby to enable the succeeding signals in the sequence to be fed in turn to the first array in the series, and with each composite signal being thus transferred successively from the first to the last array provided.

5. A method as claimed in claim 4, in which during each measurement period the occurrence of particular frequencies in the sound spectrum is used to increment respective ones of a plurality of accumulator devices, each associated with a predetermined frequency band, and in which at the end of each measurement period the contents of each accumulator device are transferred to the first array of transducers to energise the latter.

6. A method as claimed in claim 5, in which each accumulator device has a plurality of states each corresponding to a predetermined level of energisation of the associated output transducers.

7. A method as claimed in any preceding claim which includes analysing the frequency content of the input sound signal by using filters.

8. A method as claimed in any one of claims 1 to 6 which includes analysing the frequency content of the input sound signal indirectly by measuring the time intervals between successive crossings of a datum line by the signal.

9. A method as claimed in claim 8 which includes clipping the input sound signal prior to said measurement to remove amplitude information therefrom.

10. A method of analysing the frequency content of an electric sound or other signal, the method comprising the steps of clipping the signal and measuring the time intervals between successive crossings of a datum line by the clipped signal.

11. Apparatus for converting sound information into a form to be appreciated by the visual and/or tactile senses, which comprises analyser means to produce from an input sound signal a sequence of signals representative of the frequency content of the input signal at successive time instants or during successive time periods, and at least two arrays of output transducers connected to receive said sequence of signals in turn so that at any time when the transducers are energised one array represents the frequency content at one time instant or in one time period and the other or another array represents the frequency content at at least one earlier time instant or in at least one earlier time period.

12. Apparatus as claimed in claim 11, in which each array comprises a row of light sources each associated with respective adjacent frequency bands.

13. Apparatus as claimed in claim 12, in which the rows of light sources are arranged in parallel formation to define a rectangular matrix of light sources.

14. Apparatus as claimed in claim 11, in which each array comprises a plurality of electrodes to be attached to the skin and each associated with respective adjacent frequency bands.

15. Apparatus as claimed in any of claims 11 to 14, in which the transducers cover a frequency range of from the order of 30 Hz to the order of 20 kHz.

16. Apparatus as claimed in claim 15 in which said transducers cover a frequency range of from the order of 300 Hz to the order of 3 kHz.

17. Apparatus as claimed in any of claims 11 to 16, in which said analyser means determines the frequency content of the input signal indirectly by measuring the time intervals between successive crossings of a datum line by said signal.

18. Apparatus as claimed in claim 17, which includes means to clip the input signal prior to said measurement.

19. Apparatus as claimed in any of claims 11 to 18, which includes a register associated with each output transducer, connecting means linking each register in the or each other array, and respective accumulator devices connected to each series of said linked registers, whereby during a measurement period the occurrence of particular frequencies in the sound spectrum increments the appropriate accumulator devices and at the end of said period the contents of each accumulator device are transferred to the respective register in the first array.

20. Apparatus as claimed in claim 19, in which each accumulator device has a plurality of states corresponding respectively to different levels of energisation of the output transducers.

21. An apparatus for analysing the frequency content of an electric sound or other signal, the apparatus comprising means for clipping the signal and means for measuring the time intervals between successive crossings of a datum line by the clipped signal.

22. A method of converting sound information into a form to be appreciated by the visual and/or tactile senses substantially as hereinbefore described with reference to the accompanying drawings.

23. Apparatus for converting sound information into a form to be appreciated by the visual and/or tactile senses substantially as hereinbefore described with reference to the accompanying drawings.