CN2662408Y - Piano tuning indicator - Google Patents

Abstract

The utility model relates to a piano tuning indicator, which comprises a high fidelity microphone, a signal preprocessor, a multiplier, a digital low-pass filter, a signal analyzer and a display. The high fidelity microphone is connected with the signal preprocessor, the signal preprocessor is connected with the multiplier, the multiplier is connected with the low-pass filter, the digital low-pass filter is connected with the signal analyzer, and the signal analyzer is connected with the display. The utility model makes use of the high fidelity silicon microphone to test the sound of the piano, through the process of the computer collects the sounds from the piano and transforms the sounds into digital signals, and after the analysis and process gives the pitches of every piano key and the sound differences of the theoretic standard values of the corresponding keys, and therefore regulates the tune. The utility model can also be the regulating indicator for the sounds of other instruments.

Description

The piano tuning indicator

Technical field:

The utility model relates to a kind of device of testing musical sound, specifically is a kind of piano tuning indicator, belongs to the physical parameter technical field of measurement and test.

Background technology:

Piano is a kind of range broadness, the keyboard instrument that expressive force is abundant.Along with the raising of people's living standard and artistic appreciation, numerous families have had the piano of oneself.Yet owing to the manufacture characteristic of piano self or owing to aspect reasons such as other external environments, " race sound " phenomenon usually can appear in piano in use for some time, at this moment just need carry out temperament and proofread and correct, to guarantee the accuracy of its musical sound to piano.Temperament is again a kind of technical very strong work, it not only requires temperament person to be subjected to special training (being provided with the undergraduate course of special temperament as institutes such as Shenyang conservatories of music), and in the temperament process, also to guarantee absolute " peace and quiet " environment, otherwise be difficult to ensure the accuracy of the musical sound of transferring.For this reason, people once attempted to change the limitation of these traditional industries, and computer technology is introduced this field, made temperament more rely on modern scientific and technical result, reduced " human factor " as far as possible.The technology that for example in ZL:89213957, discloses.But because this patented technology is to be based upon the string of piano vibrated to be idealized as to have only fundamental frequency, be idealized as on the hypothesis basis of pure sine wave, and this and actual conditions differ greatly.So its follow-up work just is difficult to solve the problem in the reality.It can not survey two sounds of musical instrument that send simultaneously in addition, a series of defectives such as energy measurement beat tone not, and this achievement in research has lost the Practical significance in the reality.

Summary of the invention:

The purpose of this utility model is to overcome above-mentioned defective, and a kind of qualification of not doing aspect vibrations of strings is provided, and Treatment Analysis fully in the light of actual conditions can accurately be measured the piano tuning indicator of required accuracy in pitch in actual use.

The technical solution of the utility model is as follows.

A kind of piano tuning indicator is that the sound of musical instrument that microphone is heard that computerizeds control becomes digital signal, passes through a series of processing again, analyzes data, provides the correlation parameter of this sound of musical instrument at last by next " listening " sound of musical instrument of the capacitor type microphone of a high-fidelity.It comprises high-fidelity microphone, signal preprocessor, multiplier, wave digital lowpass filter, signal analyzer and display, the high-fidelity microphone is connected with signal preprocessor, signal preprocessor is connected with multiplier, multiplier is connected with wave digital lowpass filter, wave digital lowpass filter is connected with signal analyzer, and signal analyzer is connected with display.The frequency range that requires to reach when acoustic is high is 26-4200Hz.The beat tone frequency range that requires to reach when surveying beat tone is 0.01-20Hz; Described wave digital lowpass filter is the high-order elliptic filter.

Piano tuning indicator of the present utility model is a kind of indicator that is used for quantitatively illustrating the musical sound characteristics.It " listens " sound of musical instrument by the high-fidelity microphone that can cover institute's measured frequency scope, computerized control, the output of microphone is become digital signal, and through a series of processing, thereby the cent difference of indication piano pitch and theoretical audio frequency, the frequency values of " bat " sound that produces during indication tuning journey.Can indicate the degree of consistency of 2 or 3 strings on the same key of piano.

A series of Computer Processing step: as follows

1, the data acquisition of A/D conversion (sample frequency, sampling length, settings such as acquisition mode)

2, produce frequency displacement by setting value

3, through wave digital lowpass filter

4, gather (or extraction) signal data again

5, do fast fourier transform (FFT)

6, frequency coordinate is restored

7, provide the result of requirement

The mathematical principle of this technical scheme is as follows:

As everyone knows, by the A/D capture card, be exactly every through the Δ t time, computing machine is quantified as digital signal with the corresponding point on the simulating signal.It is F that its process is equivalent to frequency _sThe sampling pulse of=1/ Δ t is the modulation and the quantizing process of this simulating signal of function x (t) to continuous sound of musical instrument.

If establish: f _s-sample frequency, the Δ t-time interval, the N-sampling quantity, the T-sampling length, the n-sequence number, Δ f-frequency resolution then has relational expression:

$t=n\×\mathrm{\Δt}=\frac{n}{\mathrm{fs}}=\frac{n}{\mathrm{N\Δf}}$

T＝N×Δt

$\mathrm{fs}=\frac{1}{\mathrm{\Δt}}$

$\mathrm{\Δf}=\frac{\frac{1}{1}}{T}$

If the sound of musical instrument X (t) that microphone is heard becomes X behind A/D ₀(n),

As make it enter a multiplier being multiplied by a Function e xp (j2 π f _kT), promptly so-called signal is carried out multiple modulation, just obtained new function X (n).

The substitution of above-mentioned relation formula, then obtain:

X(n)＝X ₀(n)×exp(-j2πf _kt)

＝X ₀(n)×exp(-j2πf _knΔt)

＝X ₀(n)×exp(-j2πf _kn/fs)

＝X ₀(n)×exp[-j2πnf _k/(NΔf)]

＝X ₀(n)×exp(-j2πnL ₀/N)

＝X ₀cos(2πn?L ₀/N)-j?X ₀sin(2πn?L ₀/N)

Introduced symbol L in the middle of this ₀=f _k/ Δ f, L at this moment ₀Physical significance be that frequency spectrum is f _kThe time the spectral line sequence number.

By discrete fourier transform frequency displacement theorem as can be known, as if the discrete spectrum of representing X (n) with X (k), then X (k)=X ₀(k+L ₀).

This formula shows, after handling through frequency displacement, the spectral line shape of original signal does not change, just the frequency coordinate translation L ₀, this also means, each frequency component that contains in the signal can be near the zero point of coordinate in different frequency coordinate systems.Can become " low frequency ".If the back is with an ideal low-pass filter, just can allow certain specified frequency composition pass through, and not allow other frequency pass through after different frequency displacements be handled.Again frequency being surveyed criterion can.And piano has only 88 keys, and frequency content is spaced in whole frequency domain scope.This is just for using this technological treatment to provide the foundation and possibility.

After realizing this technical scheme with MIC microphone and PC, several pianos are tested, YAMAHA for example, KAWAI, KRAUSE, star sea piano can both prove that this technical scheme is successful.The frequency resolution that can reach is 0.01HZ, can point out the difference of pitch and 1 cent of theoretical value.Survey beat frequency, can hang down beat frequency to 0.01HZ.(index also can higher point certainly.Thought at that time that enough there is no need did again).

The utility model is not done any qualification aspect vibrations of strings, fully in the light of actual conditions Treatment Analysis can accurately be measured required accuracy in pitch in actual use.Both guaranteed its accuracy, significantly reduced the influence of artificial and extraneous factor, and also made it possess practical characteristics simple to operation by high-tech means.It relies on the condenser microphone of high-fidelity " to listen " piano sound.Utilize the Computer Processing technology, the sound of musical instrument of microphone output is collected and changes into digital signal, follow procedure is finished various analyzing and processing, finally provide how many cents of theoretical standard value difference of the pitch of each key of piano and corresponding keys number, provide the tolerance of common people's ear simultaneously, thereby instruct people the tone standard at this key number.Also can when up five degree enharmonic intervals are debugged, provide the frequency (umber of beats) of beat tone that sound of musical instrument forms, help people in beat tone changes, to catch appropriate tuning on opportunity.Because it can tell the 0.01Hz frequency difference, the consistance that can indicate two (or three) strings on the same key of people to transfer.Human factor in the temperament is reduced greatly.Simultaneously, the debugging of treble and bass area can be become more quick and easy.Be not difficult to find out that from these characteristics the utility model function and corresponding frequency domain scope also can be used as the debugging indicator of other musical sounds fully.

Description of drawings:

Fig. 1 is a circuit structure schematic diagram of the present utility model.

Fig. 2 is hardware circuit figure of the present utility model.

Embodiment:

As shown in Figure 2, the MIC that " listens " sound of musical instrument to use is condenser microphone (its frequency response of swan goose CH21 is I0-18000Hz), that carry out the A/D conversion is single-chip microcomputer SPCE061A, the serial communication of it and PC is with the UART interface of SPCE061A, carries out specific function and UART IRQ that level conversion can realize that RS232 communicates by letter by means of the 10B interface with the MAX232 chip and interrupts finishing the process of picking.The frequency displacement of back is handled, digital filter. resampling and FFT conversion are all finished by PC.

Here it is to be noted:

1) at last in the FFT process, total data all is a Useful Information, because after the frequency displacement, is with f _kDo benchmark, do new zero frequency.So half complex result of negative frequency is effective.At this moment, there is not the frequency symmetry.Negative frequency in the calculating is actually and is lower than f _kThe original frequency composition, move on to original tram to it;

2) in to data gatherer process again, raw data length there is requirement.Want to satisfy the requirement of sampling, also will defer to basic sampling law; This means that also the bandwidth of low-pass filter is not arbitrary, and take into account needs and possibility.

3) in addition, digital lowpass also is an important step.Our usefulness be 18 rank elliptic filters, low order or other mode filters are difficult to reach above-mentioned effect

Certainly, can there be multiple device to finish above-mentioned functions.For example: the MIC microphone can be used other model, but will guarantee that its frequency response enough covers the frequency domain scope of piano.The A/D capture card can be used sound card, and also available NI-DAQ-16E or other capture card (the FIFO function is preferably arranged) are finished a speech simulation signal and become digitized signal.On data processing, along with the development of single-chip microcomputer, have new product certainly, the not necessarily non-PC head it off of using.Though illustrated and described all examples of this novel enforcement, under the scope that does not break away from this structure flow process, various combinations and improvement can also have been arranged.

Claims (4)

1, a kind of piano tuning indicator, it is characterized in that: it comprises high-fidelity microphone, signal preprocessor, multiplier, wave digital lowpass filter, signal analyzer and display, the high-fidelity microphone is connected with signal preprocessor, signal preprocessor is connected with multiplier, multiplier is connected with wave digital lowpass filter, wave digital lowpass filter is connected with signal analyzer, and signal analyzer is connected with display.

2, piano tuning indicator according to claim 1 is characterized in that: the frequency range that requires to reach when acoustic is high is 26-4200Hz.

3, piano tuning indicator according to claim 1 is characterized in that: the beat tone frequency range that requires to reach when surveying beat tone is 0.01-20Hz.

4, piano tuning indicator according to claim 1 is characterized in that: described wave digital lowpass filter is the high-order elliptic filter.