CN1167561A - Apparatus and method of enhancing audio signals - Google Patents

Abstract

The present invention enhances an electronic audio signal by adding harmonics to the eletronic audio signal. The present invention includes and input stage and an output stage, with the input stage having a field inducing coil through which input electronic audio signals are to be transmitted to set up an electromagnetic field. The field receptor such that when an input electrnoic audio signal is transmitted through the inducing coil, an induced electronic audio signal is produced having an enhanced harmonic content compared to that of the input electronic audio signal.

Description

Strengthen the equipment and the method for audio signal

The present invention relates to strengthen equipment and the method for electric audio signal, particularly join equipment and method in the electric audio signal strengthening harmonic wave with the sound quality improving those signals and produced.

It has been generally acknowledged that and listen to the music, sing or other this class acoustic scene signal to noise ratio listens that to be converted into the same sound that electric audio signal then converts to after the sub-audible sound again more happy.This quality of feeling descends and has many reasons.A reason is the sound reproduction process of himself.

Many sound, especially note that we hear, normally compound.For example, the note with fundamental note or base frequency generally includes the base frequency component that is called harmonic wave.These harmonic waves have produced tone quality or the sound tonequality resemble the note, and this only is that musical instrument or other sound generating source own usually.In other words, these harmonic waves have enriched the sound that we hear.Though people's ear generally can not be told independent harmonic wave, it can feel the existence of these harmonic waves or do not exist when sound quality improves respectively or descends.Convert on-the-spot sound to equipment (for example microphone or similar devices) general insufficient record of electric audio signal and the all-mass of the on-the-spot sound of conversion.Therefore, electric audio signal does not comprise many original harmonic waves.Join in this incomplete audio signal for harmonic wave is strengthened, to have developed many sound reproductions system.But these systems are normally very complicated and costliness, and still do not reach the original quality of the sound of hearing at the scene with the sound quality that these systems produce.

Often feel that the regeneration sound Another reason lower than acoustic scene sound quality is to produce the environment with recording voice.For example, the music of place performance in the open sounds it generally being one dimension, because many sound waves are dissipated in the open and is not heard by the audience.On the other hand, sounding generally abundanter and plentiful in the music of the indoor performance of an acoustic design, and independent sound source, as musical instrument, generally more can distinguish.One of reason of this difference is that the sound that the audience hears has comprised the high-quality reverberation that produces sub-audible sound with very high-quality harmonic wave composition combination.

Not every regeneration sound all comes from the environment of acoustic design, thereby does not have the benefit of this high-quality reverberation.Even when using the environment of acoustic design, the also high-quality reverberation of possible loss in recording process, for example, when sound conversion equipment (for example microphone or similar devices) can not write down them.

Another problem of regeneration sound resemble the music is its distortion that can become when louder volume is listened to.When volume increases, the word that usually is difficult to clearly to recognize in the song and is sung or from other musical instrument, pick out a kind of musical instrument.

Also having a problem is that quality at the recording musical of indoor performance can change with respect to the position of sound source (as loud speaker) in the room with the geometry and the audience in room.When this situation occurring, music sounds better at one or several indoor ad-hoc location.The so-called melodious points in these positions (sweet spot).Therefore, for enjoying whole potentiality of institute's recording musical, the audience must remain on these melodious points.

For produce the electric audio signal (it is felt more to approach repetition and listen to a kind of like this experience of original scene sound in the environment of acoustic design) that strengthens when converting sub-audible sound to, various complexity have been developed and expensive system.The present invention is a kind of improvement on this, and it is more cheap comparatively speaking and simple.

According to the present invention, provide the method and apparatus that simply and cheaply strengthens electric audio signal in such a way: the quality of the sub-audible sound that produces from audio signal more approaches to resemble the quality of the on-the-spot original sound of hearing the environment of acoustic design.The present invention will strengthen harmonic wave and add in the electric audio signal.The sound that produces from the audio signal that strengthens according to the present invention can be in the louder volume distortion of avoiding becoming, and can eliminate or the formation of the melodious point of remarkable at least reduction.

In order to reach these purposes, according to principle of the present invention, electric audio signal sends by a magnetic coil audio power transmission system, and this system strengthens electric audio signal in such a way: feel abundanter and more plentiful from the sub-audible sound that audio signal produced that strengthens.In more detail, electric audio signal sends with electric power by an electromagnetic field inducing coil, thereby produces a field signal relevant with original electric audio signal (field signal).Then, field signal weak coupling or loosely are coupled on the field receiver, this field receiver with field signal convert enhancing to but faint electric audio signal then, this electric audio signal can be amplified in order to regenerate in resembling the conventional audio reproduction equipment of loud speaker and so on where necessary.By weak coupling or loose couplings, the electromagnetic field that only has sub-fraction to be set up by induction coil runs through or passes through field receiver.The result that the field signal of induction weakly couples to receiver forms electric audio signal, thereby and the sound that produces from this signal, the harmonic wave of wanting by adding is enhanced.

Weak coupling between induction coil and the field receiver or loose couplings can cause the signal negative distortion of well-known high boost, low cut.The present invention is based on such discovery: be accompanied by undesirable distortion of this class or degradation, add desirable harmonic wave to signal and also cause a kind of desired distortion that has or enhancing.Believe that not detecting this harmonic wave up to now as yet strengthens, out in the cold because negative distortion (promptly sacrifice low frequency, promote high frequency) strengthens this harmonic wave.Because the undesirable distortion relevant with weak coupling so is easy to set up and is well-known, and the harmonic wave of being found enhancing is unknown by the people, thus weak coupling always avoided, rather than resemble the present invention and go to utilize it like this.Induction coil of the present invention and field receiver weak coupling or loose couplings are together to promote this undesirable distortion because strange harmonic wave strengthens that comes from.

It is believed that an induction coil can be around the line of at least one circle, but induction coil is preferably around the line of many circles.Think that receiver can be line, plate, pipe or other the structure of electromagnetism conduction, but field receiver coil that many circles are arranged preferably.The field induction coil preferably has the identical number of turn with the field receiver coil, even preferably the field receiver coil has the more number of turn than an induction coil.Induction and receiver coil can be each positioned at one independently on the magnetic core or all be positioned on the single shared magnetic core.Magnetic core preferably resembles such magnetic core non-magnetic or low permeability of air, plastics and cardboard magnetic core.

According to above-mentioned situation, thereby a kind of equipment and method of simple and cheap enhancing electric audio signal are provided, so that when sound equipment reproduces sound, have the quality of the original scene sound of being heard in the environment that is tending towards in acoustic design.

Consider the following description and drawings, purpose of the present invention, feature and advantage will become more apparent.

Fig. 1 is the theory diagram of audio signal enhancement device in accordance with the principles of the present invention;

Fig. 2 is the perspective view according to an embodiment of induction coil of the present invention and field receiver coil;

Fig. 3 is the circuit diagram that strengthens equipment with the similar double-channel audio frequency signal of the equipment of Fig. 1; And

Fig. 4 is a schematic cross sectional view according to another embodiment of induction coil of the present invention and field receiver coil.

With reference to Fig. 1, show an embodiment who strengthens the system 10 of electric audio signal according to the principle of the invention herein.System 10 comprises the input stage 12, input amplifier 16 and the electromagnetic field inducing coil 18 that contain power supply 14, by this electromagnetic field inducing coil, amplifier 16 drives multifrequencies input electric audio signals, produce one with from the relevant field signal of original input signal such as microphone, wireless receiver, television audio receiver, phone receiver or the like electric audio signal source 20.System 10 comprises that also the field signal that will produce from input stage 12 converts the output stage 22 of electric audio signal to, this electric audio signal principle according to the present invention is enhanced and can be by the conventional sound generating apparatus 24 regeneration sub-audible sound that resemble loud speaker and so on, or records on the recording medium.Output stage 22 comprises that one is connected to by the field receiver 26 on the output amplifier 28 of power supply 30 power supplies.Field receiver 26 is configured to receive the very weak part of the field signal that coil 18 produces and does not introduce any a considerable amount of undesirable feedback currents in coil 18.

Input amplifier 16 is power amplifiers, its coil 18 by input stage 12 makes it to comprise that in order to convert to original input signal adds the electric audio signal of the enhancing of additional desirable harmonic wave enough to be that intensity that receiver 26 is received is amplified widely and driven input signal from source 20.Thereby weakly couple at the field signal of sensing on the coil 18 on the field receiver 26 of output stage 22.Be that receiver 26 is placed in the field of coil 18 generations, but enough distances are arranged, so that can receive the signal of enhancing and don't sense undesirable feedback in the coil 18 by electromagnetic ground.Weak coupling coil 18 and receiver 26 have formed magnetic coil audio power converting system 54.

Here think that coil 18 is single-turn circular coils of an insulated wire 34 on the magnetic core 36, receiver 26 can be line, pipe or the plate of a conduction.But comparatively ideal is that coil 18 and receiver 26 all are respectively the multiturn coils of insulation magnet-wire 34 and 44, and the number of turn is identical.Though shown coil 18 and 26 is cylinder or circle, the present invention is not limited thereto.Receiver coil 26 is on magnetic core 46, and it has formed the part of the magnetic core identical with magnetic core 36 ideally.Corresponding with from the field signal of coil 18, in receiver coil 26, produce the electric audio signal that strengthens, but because weak coupling, its amplitude compares to the input signal that drives by coil 18 very low.The signal that strengthens is very weak by receiver coil 26 time, so that any field signal that the signal that strengthens may be responded to is very weak, can not produce himself tangible feedback signal in coil 18.The output of coil 26 is connected on the output amplifier 28, and being amplified to the signal that will strengthen enough is that sound reproduction equipment 24 is used.

A little less than preferably the field signal of coil 18 induction is compared to upper frequency for lower frequency.Thereby, the lower frequency of the enhancing audio signal that receiver coil 26 produces than its higher frequency components a little less than.In other words, before amplification, compare, strengthen the height of the amplitude (power level) of audio signal front end than its low frequency end with the original input audio signal that drives by coil 18.Therefore, output amplifier 28 preferably comprises frequency shaping network 109 (see figure 3)s, it compensates (favor) low frequency, attenuate high frequency, thereby making final result and the enhancing audio signal when entering the input audio signal before the input stage 12 and leaving output stage 22 is compared, is a quite flat frequency response.

As shown in Figure 2, magnetic core 36 and 46 preferably respectively forms the part of single core components (member) 52, and coil 18 and 26 is coaxial and separate one apart from G along central shaft 48 like this.Though shown is the pipe that cardboard, plastics or other suitable material of a circular section made, magnetic core 52 can have other cross section, as rectangle, and can be acrylic acid or the enough low material of other permeability make strong.On single magnetic core 52, can see the coil 18 and 26 of energy conversion system 54 seems it is respectively that primary and secondary has consumption transformer (transformer).Promptly.Coupling between the coil 18 and 26 is very accurately weak, makes to have only the actual mutual inductance action of very little (if there is) between coil.And, think the receivers of the main field as coil 18 inductions of coil 26, and thereby relatively coil 18 place, produce obvious distortion with the enhancing that does not make input signal.Preferably use the low permeability magnetic core, this helps as the weak coupling between the coil of advantage of the present invention.In addition, one or morely be similar to 1 or uniform low permeability magnetic core such as its permeability by using, coil 18 and 26 can keep enough approaching mutually and input and output level 12 and 22 can be contained in the relative less encapsulation.Though can satisfy high magnetic permeability magnetic core even the use of permeability magnetic core by force, for keeping weak coupling, it is very big that the space between the coil becomes possibly.In addition, except coil, think that 26 of receivers should be line, pipe or other devices of one, one section permeability conduction, it receives and converts to new enhancing electric audio signal with the field of coil 18 inductions.

For the work of enhanced system 10, preferably with input stage 12 and output stage 22 good insulation on electric and on the electromagnetism (at the interface of coil 18 and 26 except the feeble field coupling of system 54).For this reason, provide independently power supply 14 and 30, respectively be with an independently ground connection at different levels 12 and 22.And, each power supply 14,30 physically with two levels keep larger distances or for example with this area known shield technology and material they are shielded from level 12,22.

Conventional audio signal source 20 (for example microphone, tape player, Disc player, wireless receiver, television audio receiver, phone receiver or the like) is typically connected on the sound generation equipment 24 resemble the loud speaker.When equipment 24 will convert sub-audible sound to from the electric audio signal in conventional source 20, the abundant and plentiful degree (quality) that the sound that is produced does not have original scene sound to be had before being recorded.The quality of the audio sound that is produced is enhanced by introduce system 10 of the present invention between source 20 and equipment 24 basically.The electric audio signal output of signal source 20 is connected on the input stage 12, and the output of output stage 22 is connected in the input of sound conversion equipment 24, and like this, any electric audio signal must be by magnetic coil audio power converting system 54 before converting sub-audible sound to.When the audience heard this sub-audible sound, its quality was strengthened to the such degree of original performance of seemingly playing live that sounds in good acoustic enviroment.Preferably use two systems 10 (being binary channels), respectively be used for each passage of stereophonic reproduction system.

Construct a binary channels version of system 10 with the available electronic unit of following commerce:

A) dual track input amplifier (16)-solid-state stereo 12W of emulation (realistic) S-20

Amplifier, model 31-B;

B) two input coils (18)-respectively are the loudspeaker coil of standard, are rated for 8 Ω and 2W;

C) two receiver coils (26)-respectively are the loudspeaker coil of standard, be rated for 8 Ω and

2W; With

D) dual track output amplifier (28)-artificial stereo sound 1.5W preamplifier, model

42-2109。

The model that above-mentioned loudspeaker coil 18,26 is taken from the production of Tandy company is the 3 inch diameter loud speakers of 40-248.Each winding 18,26 wide W (see figure 2) about 0.15 inch (0.38cm), internal diameter about 0.52 inch (1.32cm) is about 105 inches (267cm), diameters by about 30 circles and comprises that two-layer (altogether about 60 circles) magnetic line of its insulating barrier about 0.005 inch (0.013cm) forms.Every pair of winding 18,26 is co-axially mounted on the single solid-state propionic acid alkene magnetic core 50, this magnetic core have about 3/4 inch take advantage of 1/4 inch (1.9 * 0.64cm) square-sections also pass completely through two coils 18,26.Interval G between the coil 18,26 is equivalent to about 0.060 inch (0.152cm).Tandy company is production emulation amplifier also.Usually, the amplification degree of the audio signal that provides of input amplifier 16 is directly related with optimum distance G (see figure 2) between the coil 18,26.For example, other all variablees keep the same, and along with the increase of the multiplication factor of the audio signal of input amplifier 16, G finally must increase certainly at interval.As mentioned above, the also direct certainly permeability with magnetic core 52 of G changes at interval.This early implementation example of the present invention has produced the sound that strengthens but some undesirable characteristics also occurred.For overcoming these problems, constructed another binary channel embodiment of system 10, be described now with reference to Fig. 3.

With reference to Fig. 3, show the binary channel of a system 10 that comprises 10a of left side system and the identical 10b of the right system or the detailed principle example of stereo version 100 herein.System 10a and 10b share public input stage power supply 14 and public output stage power supply 30, below will be described this.Input and output level 12a, the 12b of two 10a of system and 10b are identical with 22a, 22b, therefore followingly only the circuit of the 10a of system are described in detail, and the 10b of system is identical certainly.

In more detail, input stage 12a comprise that a pair of ground (GND1) that is connected respectively to power supply 14 and input stage 12a is gone up and 10k Ω potentiometer 74 on the first electric audio frequency input 70,72.The slide plate of potentiometer 74 is connected in the noninvert input of LM383 operational amplifier 78 through 10 μ F electric capacity 76.The output 80 of amplifier 78 feeds back to its anti-phase input from the node of the series resistance 84,85 (being respectively 200 Ω and 10 Ω) of the 1/2W ground connection electric capacity 86 by one 470 μ F.The output 80 of amplifier 78 also is connected on the GND1 through the series arm of the electric capacity 90 of the resistor 88 of 1 Ω, 1/2W and 0.2 μ F.Output 80 electric capacity 92 by 2,200 μ F then is connected on the induction coil 18 of magnetic coil audio power converting system 54, to drive by coil 18 from the electric audio signal of input 70,72 and induction field signal as mentioned above.

Energy conversion system 54 comprises and is connected to a field receiver 26 on the 1k Ω potentiometer 96 that the slide plate of potentiometer is connected in the noninverting input of LM1458N operational amplifier by 10k Ω resistance 98 and 1 μ F electric capacity 101.Coil 18 and receiver 26 respectively are 8 Ω, the 2W loudspeaker coil of same standard, see the above-mentioned version of the system 10 that uses commercial available electronic unit.Energy conversion system 54.Coil 18 and receiver 26 are all used low permeability polymerization ceramic material to encapsulate fully and are reached structural complete.3M, ST.Paul, black epoxy pottery compound/adhesive DP-270 that Minnesota produces provides enough structural strengths and lower permeability.Coil 18 and 26 is encapsulated in its original column structure and the coaxial orientation shown in Figure 2, at interval G about 0.025 inch (0.0635cm).The output 104 of amplifier 102 is connected on the delivery outlet 106 that strengthens audio frequency, and this mouthful provides the electric audio signal of enhancing with the delivery outlet 108 of ground connection to reclaim equiment 24, as mentioned above.The node of resistance 98 and electric capacity 101 is connected on the output stage power supply ground (GND2) by shaping circuit 109, and shaping circuit 109 comprises the circuit branch of following three parallel connections: the series circuit of (open ended) 50k Ω potentiometer 112 of 5.1k Ω resistance 110,0.05 μ F electric capacity 111 and terminal open circuit; 0.002 μ F electric capacity 114; Series circuit with 5.1k Ω resistance 116 and 0.1 μ F electric capacity 117.

The output 104 of amplifier 102 connects through following series circuit to be got back in its anti-phase input: 499k Ω resistance 122 and 0.005 μ F electric capacity 123 in parallel; 49.9k Ω resistance 124 and 0.01 μ F electric capacity 125 in parallel; 10.0k Ω resistance 126 and 0.005 μ F electric capacity 127 in parallel; With 10.0k Ω resistance 128.The anti-phase input of output amplifier 102 (and among the 10b of system corresponding output amplifier) is connected on the voltage of voltage regulation from the pressurizer 129 of power supply 30 through the node of 1.5k Ω resistance 130 to 510 Ω resistance 132 and 5V voltage stabilizing didoe 134 and 10 μ F electric capacity 136, at node 137 places, voltage is 5V.The noninverting input of output amplifier 102 is connected on the 5V reference voltage 137 through 100k Ω resistance 138 similarly.

About power supply 14 and 30, dual transformer 140 provides the voltage of about 14V to the balance (balance) of each power supply 14 and 30, existing this is described.Input stage power supply 14 comprises a diode bridge 142, and it produces a full-wave rectification output from a 14V output of dual transformer 140.Comprise level and smooth (filtering) full-wave rectification output of circuit of 1 Ω, 1/2W resistance 144,2200 μ F electric capacity 145,10k Ω, 1/2W resistance 146 and 1 μ F electric capacity 147, give each input stage 12a and 12b with 18V unregulated power supply and ground (GND1) that a nominal is provided.Similarly, output stage power supply 30 comprises a full-wave rectifying diode bridge 150 in another 14V output that is connected to dual transformer 140.Comprise the output of the level and smooth bridge 150 of circuit of 100 Ω, 1/2W resistance 151,470 μ F electric capacity 152,10k Ω, 1/2W resistance 153 and 1 μ F electric capacity 154, with 18V that a nominal is provided not voltage of voltage regulation to pressurizer 129.The output of pressurizer 129 sends ground (GND2) to through the smoothing capacity 158 of 10 μ F and the smoothing capacity 160 of 0.01 μ F, and provides a 12V stabilized voltage power supply and ground (GND2) to each output stage 22a and 22b.Electric capacity 158 provides the filtering to low frequency, and electric capacity 160 provides the filtering to high frequency.Notice that the input amplifier 78 of each 10a of system and 10b provides and be independently-powered from power supply 14 in stand-alone integrated circuit package, and the output amplifier 102 of each output stage 22a and 22b provides in the single integrated circuit encapsulation and powers from power supply 30 jointly.

For preventing to disturb audio signal separately, preferably power supply 14,30 that port before each self-capacitance 147 and 154 is kept away from the input and output level or shields as mentioned above.In addition, the energy conversion system 54 of each path (induction coil and field receiver) also may need to shield with protection system 54 and not be subjected to any interference of not wishing outside or other reason of being subjected to.

In when work, the electric audio signal of each path is connected on separately the input port 70,72 by a standard socket or analog (not shown).As will recognizing, electric audio signal generally includes the audio frequency of wide range.Each incoming level is regulated at potentiometer 74 places, so that the incoming signal level of two paths about equally and make input amplifier 78 that input signal is amplified to possible extent and do not have amplitude limit or make the input signal distortion on the contrary.Strengthen audio signal by energy conversion system 54 then, and the signal that strengthens is adjusted level by potentiometer 96 separately and is adjusted in the desirable level and smooth frequency response by potentiometer 112 separately, and potentiometer 112 also may be used for changing shaping network 109 a little to be willing to adjust tone quality as the user.Then.The audio signal that strengthens is amplified by amplifier 102 and is connected on the sound reproduction equipment 24 that resembles another amplifier or this class of speaker system by output 106 and 108 (for example by standard sockets), and converts sub-audible sound to.In addition, equipment 24 another electric audio signal register that can be the audio signal recording that will strengthen on the recording medium (for example tape or CD) of certain form.

With reference to Fig. 4 as seen, the most handy one of magnetic coil audio power converting system 54 has than its induction coil 19 receiver coil 27 of multiturn number more.Receiver coil 27 is looped around on the cylinder magnetic core 53 according to principle of the invention manufacturing.For example, magnetic core 53 can be solid-state, makes with the low permeability plastic material, at one end has a shoulder shape flange (shoulder flange) 55.Magnetic core 53 also can be with pipe of cardboard, plastics or other suitable material (being similar to magnetic core 52) or the hollow core made without the pipe of cardboard, plastics or other suitable material.Induction coil 19 is looped around the outside of receiver coil 27.Each coil 19 and 27 has guide pillar (lead) 21a, 21b and 29a, 29b separately, and each guide pillar passes a hole that forms by flange 55.Each guide pillar 21a, 21b and 29a, 29b are suitable for being connected in the suitable circuit.Increase the number of turn in the receiver 27 by relative induction coil 19, the electric audio signal that drives by this induction coil 19 just needn't be amplified to can the signal that induction is enough big in receiver coil 27 degree.

Invention has been described and explanation though with reference to many embodiment.Though and these embodiment have been carried out quite detailed description, this does not also mean that the scope of claims is subjected to the restriction of this details or the restriction of any degree.Those skilled in the art can easily find out more improvement and modification.For example, if from the music of the electric audio signal form of Disc player or sound sends by system 100 of the present invention and final enhancing electric audio signal uses tape player/recorder to record again on the tape, can find that so the quality of the music that produces from the tape of record or sound is sensuously good than the same music or the sound that directly produce from CD.Though think that extensively disk format produces more senior sound quality than magnetic tape format, this situation still can occur.The present invention can be used for certainly to from the electric audio signal of the sound conversion equipment of reasonable tube and so on its record recording medium (as tape or CD) before, from sending (as by TV or cell phone) in the air before or be directly changed into sub-audible sound (as the time) and strengthen before in concert or performance.

Therefore, the present invention be not subjected to aspect its scope specific detail, each equipment and method and shown in and the restriction of described example.Therefore, can not depart from the essence of basic inventive idea of the present invention and scope and come manufacturing equipment according to this details.

Claims (14)

1, strengthen the equipment of electric audio signal quality, comprising:

Input stage with induction coil, the electric audio signal of input sends to set up an electromagnetic field by the field induction coil; With

Output stage with an electromagnetic field receiver and an output, described induction coil with described electromagnetic field receiver weak coupling be in the same place, like this when the input electric audio signal sends by described induction coil, provide and import electric audio signal and compare the enhancing electric audio signal of harmonic wave composition with enhancing in described output place.

2, the equipment of claim 1, described induction coil has many circles.

3, the equipment of claim 2, described electromagnetic field receiver are field receiver coils that many circles are arranged.

4, the equipment of claim 3, described the induction coil of the turn ratio of described field receiver coil many.

5, the equipment of claim 3, described coil is at least one low permeability magnetic core.

6, the equipment of claim 5, described at least one low permeability magnetic core have approximate uniform permeability.

7, the equipment of claim 1, described electromagnetic field receiver are at least in the group of being made up of a pipe, one section line, winding and one flat plate.

8, the equipment of claim 1 comprises a frequency of offsetting the caused undesirable frequency shaping of described weak coupling shaping network again.

9, the equipment of claim 1 comprises that an electric audio signal that makes described enhancing is processed into the amplifier of sub-audible sound.

10, strengthen the electric audio signal method for quality, may further comprise the steps:

At least one input electric audio signal is provided;

At least one input electric audio signal sends by a field induction coil with this, thereby sets up at least one electromagnetic field; With

This at least one electromagnetic field is weakly coupled on the electromagnetic field receiver, in field receiver, to produce at least one compares the harmonic wave composition with an enhancing with the content of input electric audio signal enhancing electric audio signal.

11, the method for claim 10, further comprising the steps of:

The electric audio signal of this at least one enhancing is processed into sub-audible sound.

12, the method for claim 10, further comprising the steps of:

The electric audio signal of described at least one enhancing is recorded on the recording medium.

13, a kind of recording medium that has write down at least one enhancing electric audio signal that writes down by the method for claim 12 thereon.

14, the method for claim 10 comprises one in the electric audio signal of at least one input electric audio signal and at least one enhancing or another or the two is carried out shaping again to offset the step of the caused undesirable frequency shaping of weak coupling.

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