EP0580579B1 - Noise control apparatus - Google Patents

Noise control apparatus Download PDF

Info

Publication number
EP0580579B1
EP0580579B1 EP91920600A EP91920600A EP0580579B1 EP 0580579 B1 EP0580579 B1 EP 0580579B1 EP 91920600 A EP91920600 A EP 91920600A EP 91920600 A EP91920600 A EP 91920600A EP 0580579 B1 EP0580579 B1 EP 0580579B1
Authority
EP
European Patent Office
Prior art keywords
duct
enclosure
transmission line
chamber
noise
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP91920600A
Other languages
German (de)
French (fr)
Other versions
EP0580579A4 (en
EP0580579A1 (en
Inventor
Khosrow Eghtesadi
William John Joseph Hoge
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Noise Cancellation Technologies Inc
Original Assignee
Noise Cancellation Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Noise Cancellation Technologies Inc filed Critical Noise Cancellation Technologies Inc
Priority to AT91920600T priority Critical patent/ATE167775T1/en
Publication of EP0580579A1 publication Critical patent/EP0580579A1/en
Publication of EP0580579A4 publication Critical patent/EP0580579A4/en
Application granted granted Critical
Publication of EP0580579B1 publication Critical patent/EP0580579B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2838—Enclosures comprising vibrating or resonating arrangements of the bandpass type
    • H04R1/2842—Enclosures comprising vibrating or resonating arrangements of the bandpass type for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/30—Combinations of transducers with horns, e.g. with mechanical matching means, i.e. front-loaded horns

Definitions

  • This invention relates to noise control apparatus.
  • the simplest form of a loudspeaker system is the direct radiator.
  • a loudspeaker radiates sound directly from the enclosure aperture(s)--the driver diaphragm and, in the case of vented-box systems, a vent or port. There are no additional devices through which the sound passes.
  • a transmission line loudspeaker adds an additional device, such as a horn for impedance matching, through which some or all of the sound passes.
  • Prior forms of transmission line systems may be divided into three classes.
  • a type A transmission line system consists of a closed-box direct radiator loudspeaker with a transmission line added to the driver aperture. All radiated sound passes through the transmission line.
  • a Type B or C system consists of a direct radiator system with the transmission line coupled to the back chamber of the enclosure. Both the Type B or Type C form exhibit the fault that the transmission line presents an acoustical short circuit to the back of the driver at least at some frequencies. This can cause serious dips in the system response.
  • US-A-4665549 discloses acoustic attenuation apparatus for a duct which guides an acoustic wave.
  • a silencer is provided for passively attenuating the acoustic wave in the duct, and a cancelling speaker is provided within the silencer.
  • the combination provides hybrid active/passive combined attenuation.
  • Various rectangular and circular structures are disclosed, together with multi-path and multi-speaker arrangements.
  • US-A-4875546 discloses a loudspeaker for a hi-fi audio system having means for acoustically impeding excursion of the transducer diaphragm and means for acoustically attenuating the output of acoustic vibrations of frequencies above a preselected frequency.
  • the loudspeaker includes first and second subchambers separated by a dividing wall in which the transducer is mounted.
  • a first port acoustically couples the first subchamber with the second subchamber and a second port acoustically couples the second subchamber with the outside environment surrounding the loudspeaker.
  • the improved performance is roughly analogous to that seen in a vented-box direct radiator system as compared to a closed-box system. Either the efficiency or the bandwidth may be increased; or the system size may be decreased; or a tradeoff may be made among these possible benefits.
  • the present invention provides noise control apparatus according to Claim 1.
  • Noise control apparatus according to the pre-characterising portion of Claim 1 is known from the abstract of JP-A-2072395.
  • the transmission characteristics of the system using a horn will be determined in great measure by the horn and the acoustic load it presents to the front chamber, but will, in general, be high-pass in nature.
  • the transmission characteristics of the short tube system will be band-pass in nature.
  • the driver and the vented-box portion of the enclosure will provide a 4-pole high-pass response, and the front chamber and the outlet tube will provide a 2-pole low-pass response.
  • a preferred arrangement of the apparatus is particularly useful for active noise cancellation applications such as exhaust mufflers or duct silencers.
  • the pipe or duct through which the noisy signal is flowing passes through the enclosure and exits through the outlet tube.
  • the end of the noisy pipe or duct is aligned with the end of the loudspeaker and the two are coaxial.
  • the antinoise signal radiated by the loudspeaker during the active cancellation is coaxial with the noise.
  • Very good cancellation may be obtained at frequencies with wavelengths which are long compared to the size of the outlet.
  • FIG. 2 shows an electrodynamic loudspeaker driver 1 mounted in an enclosure 2 so that one side of the driver diaphragm radiates sound into the front chamber of the enclosure 3.
  • the sound from the other side of the driver passes through the acoustic phase inverter comprising the back chamber 4 and the inner vent 5 which connects the front and back chambers.
  • the total system output consists of the sum of the front wave and the phase corrected back wave flowing through the front chamber and out via the transmission line 6.
  • FIG. 1 shows the basic signal flow graph of the system using an electrodynamic driver 1.
  • Electric potential E g is applied accross the driver voice coil which has a resistance R E and a resulting current I VC flows.
  • the electrodynamic coupling B1 of the motor causes a driving force.
  • the sum of this force and the various reaction forces in the system gives the total force driving the diaphragm F D .
  • This force accelerates the diaphragm at a rate inversely proportional to the moving mass M MS of the driver.
  • the resulting acceleration of the diaphragm a D is integrated once with respect to time (the 1/s operation in the LaPlace domain) to find the velocity of the diaphragm u D and a second time to find the displacement of the diaphragm x D .
  • moving the diaphragm results in some reaction forces.
  • an opposing force inversely proportional to the mechanical compliance C MS of the driver is added to the total force F D .
  • Another opposing force results from the motion through the mechanical losses R MS of the system and is equal to the product of R MS and u D .
  • This volume velocity U D is equal to the product of the diaphragam velocity u D and its effective area S D .
  • This volume velocity is one of the components of the total flow into the front chamber U F .
  • the conservation of matter requires that the flow into the back chamber U B across the boundary between it and the front chamber be equal to U F but opposite in polarity.
  • the volume velocity U B pressurizes the back chamber 4 .
  • the acoustic pressure of the back chamber p B is equal to the integral of U B with respect to time divided by the acoustic compliance to the back chamber C AB . This pressure exerts another reaction force against the back of the diaphragm which is equal to the pressure p B times the diaphragm area S D . This is another component of F D .
  • the analysis of the system is similar, except that the line impedance is simplified because the short tube presents a lumped parameter element.
  • the output flow U O is equal to the front chamber pressure p F integrated with respect to time and divided by the acoustic mass of the outlet vent M AF .
  • the opposing pressure component of p F results from the flow losses in the outlet R AF .
  • FIGS. 5 to 8 show views of a practical loudspeaker system using the present invention which has particular application in active noise control systems.
  • a flow tube 7 containing for the noisy flow such as the exhaust of an engine
  • a drain tube 8 has been added between the front and back chamber so that water or other liquids trapped in the back chamber may escape. If the loudspeaker were used in an active noise cancellation system on a vehicle and if the vehicle were driven through deep water, the muffler could be flooded. The drain tube would allow the trapped water to flow out of the back chamber.
  • the drain tube must be sized so that it acts as an acoustic mass rather than an acoustic leak between the chambers. Its mass must either be considered when adjusting the enclosure tuning or be trivial compared to the inner vent 5 so that the effect of the drain may be ignored.
  • FIG. 9 shows an apparatus using the present invention which also has particular application for active noise control.
  • the- short tube 6 is formed by the area between the heat shield plate 17 and the connection to the noisy duct 7 .
  • a long, narrow tube 9 allows outside air to enter the enclosure.
  • This tube like the drain tube discussed above, should be sized so that it has no adverse effect on the system acoustic performance. It may enter the enclosure through either the front or back chamber. Air is forced through the system because of the venturi-like detail 10 in the noisy duct. The flow through the duct over the "venturi” causes a low pressure region which "draws" the outside air. This air may be useful for cooling or removal of corrosive gases.
  • FIG. 10 there is shown the general form of the Vented Box Bandpass Loudspeaker (VBBP) configuration.
  • Fig. 11 shows the simplified acoustical analogous circuit of the Vented Box Bandpass Loudspeaker (VBBP) configuration.
  • P g (S 3 C AS M AB C AB ) ⁇ S 6 M AS C AS M AP C
  • P o (S) sM AP U o

Landscapes

  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Exhaust Silencers (AREA)
  • Circuit For Audible Band Transducer (AREA)

Description

This invention relates to noise control apparatus.
The simplest form of a loudspeaker system is the direct radiator. Such a loudspeaker radiates sound directly from the enclosure aperture(s)--the driver diaphragm and, in the case of vented-box systems, a vent or port. There are no additional devices through which the sound passes.
A transmission line loudspeaker adds an additional device, such as a horn for impedance matching, through which some or all of the sound passes. Prior forms of transmission line systems may be divided into three classes. A type A transmission line system consists of a closed-box direct radiator loudspeaker with a transmission line added to the driver aperture. All radiated sound passes through the transmission line. A Type B or C system consists of a direct radiator system with the transmission line coupled to the back chamber of the enclosure. Both the Type B or Type C form exhibit the fault that the transmission line presents an acoustical short circuit to the back of the driver at least at some frequencies. This can cause serious dips in the system response.
US-A-4665549 discloses acoustic attenuation apparatus for a duct which guides an acoustic wave. A silencer is provided for passively attenuating the acoustic wave in the duct, and a cancelling speaker is provided within the silencer. The combination provides hybrid active/passive combined attenuation. Various rectangular and circular structures are disclosed, together with multi-path and multi-speaker arrangements.
JP-A-2072395 discloses in its abstract an active noise control method for application to a large noise of low frequency including connecting a branch pipe to a noise propagation conduit and generating a control sound through the branch pipe. The branch pipe is fitted midway along the duct which connects a noise source such as an air blower and an air compressor to an air intake (or air outlet). The control sound is generated by a speaker installed at an end of the branch pipe.
US-A-4875546 discloses a loudspeaker for a hi-fi audio system having means for acoustically impeding excursion of the transducer diaphragm and means for acoustically attenuating the output of acoustic vibrations of frequencies above a preselected frequency. The loudspeaker includes first and second subchambers separated by a dividing wall in which the transducer is mounted. A first port acoustically couples the first subchamber with the second subchamber and a second port acoustically couples the second subchamber with the outside environment surrounding the loudspeaker.
There is described herein an improved form of the Type A system in which the signals from both the drive aperture and the port of a vented-box direct radiator system are combined to drive the transmission line. The original form of the Type A system prevents the back wave from the driver diaphragm from interfering with the front wave by trapping the back wave in the closed cavity behind the driver. The improved system passes the back wave through an acoustic phase inverter so that it may be combined with the output from the front side of the driver. This doubles the energy available to drive the transmission line. This improvement should not be confused with hybrid systems which use a vented-box system with the transmission line coupled to either the driver aperture or the vent but not both.
The improved performance is roughly analogous to that seen in a vented-box direct radiator system as compared to a closed-box system. Either the efficiency or the bandwidth may be increased; or the system size may be decreased; or a tradeoff may be made among these possible benefits.
The present invention provides noise control apparatus according to Claim 1.
Noise control apparatus according to the pre-characterising portion of Claim 1 is known from the abstract of JP-A-2072395.
In one preferred arrangement of the apparatus one or more electrodynamic loudspeaker drivers is installed in a vented-box direct radiator enclosure, and a cover is added to the front of the enclosure. This cover forms a front chamber into which both the driver and the vent radiate sound. The sound passes through the front chamber and into the transmission line. For applications requiring high efficiency over a wide bandwidth the transmission line may be a horn. However, a compact system might use a short tube, configured to produce a desired band-pass frequency response characteristic.
The transmission characteristics of the system using a horn will be determined in great measure by the horn and the acoustic load it presents to the front chamber, but will, in general, be high-pass in nature. The transmission characteristics of the short tube system will be band-pass in nature. The driver and the vented-box portion of the enclosure will provide a 4-pole high-pass response, and the front chamber and the outlet tube will provide a 2-pole low-pass response.
A preferred arrangement of the apparatus is particularly useful for active noise cancellation applications such as exhaust mufflers or duct silencers. In this arrangement the pipe or duct through which the noisy signal is flowing passes through the enclosure and exits through the outlet tube. The end of the noisy pipe or duct is aligned with the end of the loudspeaker and the two are coaxial. Thus, the antinoise signal radiated by the loudspeaker during the active cancellation is coaxial with the noise. Very good cancellation may be obtained at frequencies with wavelengths which are long compared to the size of the outlet.
Another preferred arrangement of the apparatus which also has particular application in active noise cancellation systems is similar to that described immediately above. However, in this arrangement the pipe or duct containing the noisy flow does not pass through the loudspeaker. Instead, the loudspeaker outlet tube connects the loudspeaker front chamber to the pipe as a tee fitting into the pipe. In this case, the pipe need not end at the point where the noise and antinoise are mixed. This arrangement is useful for "in duct" cancellation.
The invention will now be further described by way of examples, with reference to the accompanying drawings, in which:
  • FIGS. 1 and 3 are signal flow graphs of the improved loudspeaker with a long transmission line and a short outlet tube,
  • FIGS. 2 and 4 are simplified drawings of the invention, and
  • FIGS. 5 to 9 show two ways in which the invention may be put to practical use in noise cancellation applications.
  • FIG. 10 shows a general form of a vented box bandpass loudspeaker.
  • FIG. 11 shows a simplified acoustical analogous circuit.
    • Consider first FIGS. 1 and 2. FIG. 2 shows an electrodynamic loudspeaker driver 1 mounted in an enclosure 2 so that one side of the driver diaphragm radiates sound into the front chamber of the enclosure 3. The sound from the other side of the driver passes through the acoustic phase inverter comprising the back chamber 4 and the inner vent 5 which connects the front and back chambers. The total system output consists of the sum of the front wave and the phase corrected back wave flowing through the front chamber and out via the transmission line 6.
    FIG. 1 shows the basic signal flow graph of the system using an electrodynamic driver 1. Electric potential Eg is applied accross the driver voice coil which has a resistance RE and a resulting current IVC flows. The electrodynamic coupling B1 of the motor causes a driving force. The sum of this force and the various reaction forces in the system gives the total force driving the diaphragm FD. This force accelerates the diaphragm at a rate inversely proportional to the moving mass MMS of the driver. The resulting acceleration of the diaphragm aD is integrated once with respect to time (the 1/s operation in the LaPlace domain) to find the velocity of the diaphragm uD and a second time to find the displacement of the diaphragm xD. Now, moving the diaphragm results in some reaction forces. As the diaphragm is displaced against the mechancial springs in its suspension, an opposing force inversely proportional to the mechanical compliance CMS of the driver is added to the total force FD. Another opposing force results from the motion through the mechanical losses RMS of the system and is equal to the product of RMS and uD. Also, as the voice coil moves through the magnetic field of the motor a back emf is generated which tends to oppose the driving potential. This back emf, which is equal to the electromagnetic coupling B1 times the diaphragm velocity uD, sums with the input potential Eg to give the voice coil potential EVC.
    As the diaphragm moves, the front side pushes against the surrounding air and a flow into the front chamber 3 results. This volume velocity UD is equal to the product of the diaphragam velocity uD and its effective area SD. This volume velocity is one of the components of the total flow into the front chamber UF . The conservation of matter requires that the flow into the back chamber UB across the boundary between it and the front chamber be equal to UF but opposite in polarity. The volume velocity UB pressurizes the back chamber 4. The acoustic pressure of the back chamber pB is equal to the integral of UB with respect to time divided by the acoustic compliance to the back chamber CAB . This pressure exerts another reaction force against the back of the diaphragm which is equal to the pressure pB times the diaphragm area SD . This is another component of FD .
    For the purpose of an orderly description of the system, assume that the inner vent 5 is blocked. This is equivalent to the unimproved form of the transmission line loudspeaker. The flow into the front chamber 3 pressurizes it. This component of the front chamber acoustic pressure pF is equal to the integral of UF with respect to time divided by the acoustic compliance of the front chamber CAF . The front chamber pressure drives the flow through the transmision line 6 at a rate inversely proportional to the input reactance XAT of the line. The resistive part of the line impedance RAT causes a reaction pressure which is -also a component of pF . XAT and RAT are frequency dependent line characteristics. The-front chamber pressure also causes a reaction force on the diaphragm equal to pF times SD . This is another component of FD .
    Now, assume that the inner vent 5 is no longer blocked. The pressure in the back chamber pB will drive a flow through the inner vent with a volume velocity Up which is equal to the integral of the pressure pB with respect to time divided by the acoustic mass of the vent MAP . The volume velocity components UD and Up now add to form the total flow into the front chamber UF which, in turn, drives the system output UO .
    In the arrangement of FIGS. 3 and 4, the analysis of the system is similar, except that the line impedance is simplified because the short tube presents a lumped parameter element. In this case, the output flow UO is equal to the front chamber pressure pF integrated with respect to time and divided by the acoustic mass of the outlet vent MAF . The opposing pressure component of pF results from the flow losses in the outlet RAF .
    Analysis of the signal flow graphs yields the approriate design equations which allow the correct driver and enclosure parameters to specify for a desired system.
    FIGS. 5 to 8 show views of a practical loudspeaker system using the present invention which has particular application in active noise control systems. In this apparatus an additional component, a flow tube 7 containing for the noisy flow (such as the exhaust of an engine), has been added. Also, a drain tube 8 has been added between the front and back chamber so that water or other liquids trapped in the back chamber may escape. If the loudspeaker were used in an active noise cancellation system on a vehicle and if the vehicle were driven through deep water, the muffler could be flooded. The drain tube would allow the trapped water to flow out of the back chamber. The drain tube must be sized so that it acts as an acoustic mass rather than an acoustic leak between the chambers. Its mass must either be considered when adjusting the enclosure tuning or be trivial compared to the inner vent 5 so that the effect of the drain may be ignored.
    FIG. 9 shows an apparatus using the present invention which also has particular application for active noise control. In this instance, the- short tube 6 is formed by the area between the heat shield plate 17 and the connection to the noisy duct 7. A long, narrow tube 9 allows outside air to enter the enclosure. This tube, like the drain tube discussed above, should be sized so that it has no adverse effect on the system acoustic performance. It may enter the enclosure through either the front or back chamber. Air is forced through the system because of the venturi-like detail 10 in the noisy duct. The flow through the duct over the "venturi" causes a low pressure region which "draws" the outside air. This air may be useful for cooling or removal of corrosive gases.
    The analysis and derivation of the analog circuit of the Vented Box Bandpass Loudspeaker is as follows: The symbols used in Figures 10 and 11 and in the calculations are:
    LIST OF SYMBOLS
    CAB
    Acoustic compliance of Rear Box
    CAP
    Acoustic compliance of Front Box
    CAS
    Acoustic compliance of Driver (Loudspeaker VAS=PoC2CAS)
    MAP
    Acoustic mass of Front Port
    MAS
    Acoustic mass of Driver
    MAB
    Acoustic mass of Internal Port
    RAS
    Acoustic Resistance of Driver
    RE
    Electrical Resistance of Driver voice coil
    SD
    Driver Diaphragm, M2
    VB
    Volume of Rear Closed Box (M3) (VB=PoC2CAB)
    VP
    Volume of Front Box (M3) (Vp=PoC2CAP)
    Vd
    Peak displacement volume driver diaphragm (SDXM)
    Po
    Mas densily of air (7.18 kg/m3)
    C
    Speed of sound in air (345 m/sec)
    Xm
    Peak linear displacement of driver diaphragm
    Sp
    Area of the front port
    SB
    Area of the internal port
    B
    Magnetic flux density in driver airgap
    l
    length of voice coil in the airgap of driver
    Uo
    Volume velocity at the front port
    UAB
    Volume velocity at the internal port
    UF
    Volume velocity inside the front box (UF=US+UAB)
    UB
    Volume velocity inside the rear box (UB=-UF)
    US
    Volume velocity generated at the source
    Pg
    Pressure generator (equivalent)
    Eg
    Input voltage to the loudspeaker
    Speaker Parameters
    fs (Ts= 1απƒs ) Free Air Resonance frequency
    QES
    Electro-Magnetic Q at fs
    Qms
    Mechanical Q at fs
    Qts
    Total Q at
    Figure 00090001
    Vas
    Volume of air having sam acoustic compliance as driver suspension
    Vd
    Peak displacement volume of diaphragm (=SDXM)
    SD
    Effective diaphragm area
    Xm
    Peak linear displacement of diaphragm
    Referring now to Fig. 10, there is shown the general form of the Vented Box Bandpass Loudspeaker (VBBP) configuration. Fig. 11 shows the simplified acoustical analogous circuit of the Vented Box Bandpass Loudspeaker (VBBP) configuration. The terms Ro and Pg are determined by the following formulae: Ro = (BL)2 RESD 2 Pg = Eg(BL)RSD
    In the following circuit analysis, assumptions are made that there is a lossless enclosure (internal box resistance = O and leakage resistance =a) and that the voice coil inductance is small (LF≈O)
    The circuit analysis is as follows:
    Figure 00100001
    (2)   UF-Uo sCAP = sMAP-Uo (3)   sMABUAB+UF sCAB +sMAPUo=0 (4)   From Equation (2) UF=(1+S2MAPCAP)Uo US+UAB=UF (5) Us=UF-UAB
    From equation (3)
    Figure 00100002
    Figure 00110001
    Figure 00110002
    Substitute Equations (4) and (6) into the Equation (1)
    Figure 00110003
    (8)   Pg(S3CASMABCAB)={S6MASCASMAPCAPMABCAB+ s4MASCASMABCAB + S4MASCASMAPCAP+S4MASCASMAPCAB +S2MASCAS+S5CASRAtMAPCAPMABCAB+S3CASRATMABCAB +S3CASRATMAPCAP+S3CASRATMAPCAB+SCASRAT +S4MAPCAPMABCAB+S2(MABCAB+MAPCAP+MAPCAB) +1+S2MABCAB+S4CAPMABCABMAP+S4CASMAPMABCAB}Uo (9)   Pg(S3CASMABCAB)={S6MASCASMAPCAPMABCAB+ S5CASRATCAPMABCAB+ S4 (MASCASMABCAB+MASCASMAPCAP+ MASCASCAB+MAPCAPMABCAB+MABCABMAPCAP +MABCABMAPCAS)+S3CASRAT(MAPCAP+MAPCAB+ MABCAB)+S2(MASCAS+2MABCAB+MAPCAP+MAPCAB) +SCASRAT+1}Uo
    ASSUMPTIONS
    (10)   Ts 2= 1Ws 2 = MASCAS (11)   TB 2= 1WB 2 = MABCAB (12)   Tp 2= 1Wp 2 = MAPCAP (13)   Tps 2= 1Wps 2 = MAPCAS (14)   TPB 2= 1WPB 2 = MAPCAB (15)   RAT=Ro+RAS = P0C2 WsVASQES + PoC2 WsVASQMS = 1CASWsQts (16)   CASRAT = 1WsQts = Ts Qts (17)   Po(S) = sMAPUo
    SYSTEM TRANSFER FUNCTION
    (18)   G(s) = sMAPUo Pg = Po(s)Pg(s) (19)   G(s) =bs4 S6 + a5S5 + a4S4 + a3S3 + a2S2 + a1S1 + a0 when, (20)   a5= TB 2Tp 2 WsQts x 1Ts 2TB 2Tp 2 = TB 2Tp 2Ts Ts 2TB 2Tp2Qts = 1TsQts = Ws Qts (21)   a4 = 1Ts 2TB 2Tp 2 (Ts 2TB 2+Ts 2Tp 2+Ts 2TpB 2+2Tp 2TB 2+TB 2Tps 2) = 1Tp 2 + 1TB 2 + TpB 2 TB 2Tp2 + 2Ts 2 + Tps 2 Ts 2Tp 2 = Wp 2+WB 2 + WB 2Wp 2 WpB 2 + 2Ws 2 + Ws 2Wp 2 Wps 2
    Figure 00130001
    (23)   a2 1Ts 2TB 2+Tp 2 (Ts 22TB 2+Tp 2+TpB) = = (WB 2Wp 2+2Ws 2Wp 2+Ws 2WB 2+ Ws 2WB 2Wp 2 WPB 2 ) (24)   a1= Ts Qts x 1Ts 2TB2Tp 2 = WsWB 2Wp 2 Qts (25)   ao = 1Ts 2TB 2Tp 2 = Ws 2WB 2Wp 2 (26)   b= MAPCASMABCAB Ts 2TB 2Tp 2 = Tps 2TB 2 Ts 2TB 2Tp 2 = Tps 2 Ts 2Tp 2 = Ws 2Wp 2 Wps 2
    It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the claims.

    Claims (8)

    1. Noise control apparatus comprising:
      an enclosure means (2);
      at least one loudspeaker driver means (1) mounted in the enclosure means (2); and
      a duct means (7), the enclosure means being arranged to generate anti-noise to noise in the duct means (7);
         characterised in that:
      the enclosure means has front (3) and back (4) chamber means connected by a conduit means (5);
      the loudspeaker driver means is adapted to produce a front and back wave so that at a desired frequency the back wave is constructively summed with the front wave in the front chamber means (3); and
      transmission line means (6) is provided attached to said front chamber means (3) and acoustically coupled to the duct means (7), said transmission line means (6) comprising the only outlet of anti-noise from the enclosure means to the duct means (7).
    2. Apparatus as claimed in Claim 1, in which the transmission line means is a horn.
    3. Apparatus as claimed in Claim 1, in which the transmission line means is a short tube means.
    4. Apparatus as claimed in Claim 1, 2 or 3, in which the duct means (7) passes through the enclosure means (2) and exits through the transmission line means (6) for the purpose of noise control.
    5. Apparatus as claimed in any of the preceding claims, in which a drain means (8) is provided between the front and back chamber means to allow trapped liquids to drain from the back chamber, the drain means preferably being in the form of a hole or a tube.
    6. Apparatus as claimed in Claim 3, or Claim 4 or 5 as dependent on Claim 3, in which the short tube means (6) is formed by the area between a plate means in the front chamber means and the connection to the duct means.
    7. Apparatus as claimed in any of the preceding claims, in which a ventilation tube means (9) is connected between either the front or the back chamber means and the outside air and a venturi-like structure means is in the duct means in order to create a low pressure region to draw outside air through the system.
    8. Apparatus as claimed in any of the preceding claims, in which said conduit means (5) comprises a hole connecting said front and back chambers.
    EP91920600A 1991-04-19 1991-04-19 Noise control apparatus Expired - Lifetime EP0580579B1 (en)

    Priority Applications (1)

    Application Number Priority Date Filing Date Title
    AT91920600T ATE167775T1 (en) 1991-04-19 1991-04-19 NOISE CANCELLATION DEVICE

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    PCT/US1991/002731 WO1992019080A1 (en) 1991-04-19 1991-04-19 Improvements in and relating to transmission line loudspeakers
    CA002108696A CA2108696A1 (en) 1991-04-19 1991-04-19 Improvements in and relating to transmission line loudspeakers

    Publications (3)

    Publication Number Publication Date
    EP0580579A1 EP0580579A1 (en) 1994-02-02
    EP0580579A4 EP0580579A4 (en) 1994-06-15
    EP0580579B1 true EP0580579B1 (en) 1998-06-24

    Family

    ID=25676762

    Family Applications (1)

    Application Number Title Priority Date Filing Date
    EP91920600A Expired - Lifetime EP0580579B1 (en) 1991-04-19 1991-04-19 Noise control apparatus

    Country Status (8)

    Country Link
    EP (1) EP0580579B1 (en)
    JP (1) JPH06508445A (en)
    CA (1) CA2108696A1 (en)
    DE (1) DE69129664T2 (en)
    DK (1) DK0580579T3 (en)
    ES (1) ES2118093T3 (en)
    HK (1) HK1011163A1 (en)
    WO (1) WO1992019080A1 (en)

    Cited By (5)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    US9564146B2 (en) 2014-08-01 2017-02-07 Bongiovi Acoustics Llc System and method for digital signal processing in deep diving environment
    US9998832B2 (en) 2015-11-16 2018-06-12 Bongiovi Acoustics Llc Surface acoustic transducer
    US10069471B2 (en) 2006-02-07 2018-09-04 Bongiovi Acoustics Llc System and method for digital signal processing
    US10158337B2 (en) 2004-08-10 2018-12-18 Bongiovi Acoustics Llc System and method for digital signal processing
    US10313791B2 (en) 2013-10-22 2019-06-04 Bongiovi Acoustics Llc System and method for digital signal processing

    Families Citing this family (21)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    WO1995030393A1 (en) * 1994-05-10 1995-11-16 Noise Cancellation Technologies, Inc. Active noise cancelling muffler
    US6504938B1 (en) * 2000-10-06 2003-01-07 Logitech Europe S.A. Dual-chamber loudspeaker
    US10848118B2 (en) 2004-08-10 2020-11-24 Bongiovi Acoustics Llc System and method for digital signal processing
    US11431312B2 (en) 2004-08-10 2022-08-30 Bongiovi Acoustics Llc System and method for digital signal processing
    US8284955B2 (en) 2006-02-07 2012-10-09 Bongiovi Acoustics Llc System and method for digital signal processing
    US11202161B2 (en) 2006-02-07 2021-12-14 Bongiovi Acoustics Llc System, method, and apparatus for generating and digitally processing a head related audio transfer function
    US10848867B2 (en) 2006-02-07 2020-11-24 Bongiovi Acoustics Llc System and method for digital signal processing
    US10701505B2 (en) 2006-02-07 2020-06-30 Bongiovi Acoustics Llc. System, method, and apparatus for generating and digitally processing a head related audio transfer function
    EP1994793B1 (en) * 2006-03-15 2014-10-08 Thomas J. Danley Sound reproduction with improved low frequency characteristics
    DE102011084567C5 (en) * 2011-10-14 2019-08-14 Eberspächer Exhaust Technology GmbH & Co. KG Active muffler
    US9883318B2 (en) 2013-06-12 2018-01-30 Bongiovi Acoustics Llc System and method for stereo field enhancement in two-channel audio systems
    US9264004B2 (en) 2013-06-12 2016-02-16 Bongiovi Acoustics Llc System and method for narrow bandwidth digital signal processing
    US10820883B2 (en) 2014-04-16 2020-11-03 Bongiovi Acoustics Llc Noise reduction assembly for auscultation of a body
    US10639000B2 (en) 2014-04-16 2020-05-05 Bongiovi Acoustics Llc Device for wide-band auscultation
    US9615813B2 (en) 2014-04-16 2017-04-11 Bongiovi Acoustics Llc. Device for wide-band auscultation
    US9479861B2 (en) * 2014-06-26 2016-10-25 Anthony Allen BISSET Compact wideband bass and midrange horn-loaded speaker system
    US9638672B2 (en) 2015-03-06 2017-05-02 Bongiovi Acoustics Llc System and method for acquiring acoustic information from a resonating body
    US9906867B2 (en) 2015-11-16 2018-02-27 Bongiovi Acoustics Llc Surface acoustic transducer
    CN112236812A (en) 2018-04-11 2021-01-15 邦吉欧维声学有限公司 Audio-enhanced hearing protection system
    WO2020028833A1 (en) 2018-08-02 2020-02-06 Bongiovi Acoustics Llc System, method, and apparatus for generating and digitally processing a head related audio transfer function
    CN113504663B (en) * 2021-07-23 2023-04-25 歌尔科技有限公司 Sound production module, sound production module silencing method and intelligent glasses

    Family Cites Families (10)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    JPS5031801A (en) * 1973-07-20 1975-03-28
    JPS5789393A (en) * 1980-11-17 1982-06-03 Bose Corp Controller for low end response for loudspeaker system
    US4473906A (en) * 1980-12-05 1984-09-25 Lord Corporation Active acoustic attenuator
    US4549631A (en) * 1983-10-24 1985-10-29 Bose Corporation Multiple porting loudspeaker systems
    US4616731A (en) * 1984-03-02 1986-10-14 Robinson James R Speaker system
    US4665549A (en) * 1985-12-18 1987-05-12 Nelson Industries Inc. Hybrid active silencer
    US4875546A (en) * 1988-06-02 1989-10-24 Teledyne Industries, Inc. Loudspeaker with acoustic band-pass filter
    JPH0787628B2 (en) * 1989-02-22 1995-09-20 株式会社ケンウッド Speaker system for bass reproduction
    US5025885A (en) * 1989-07-14 1991-06-25 Bose Corporation Multiple chamber loudspeaker system
    JP4862491B2 (en) * 2005-05-25 2012-01-25 東レ株式会社 Flocking piles and flocking products

    Cited By (5)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    US10158337B2 (en) 2004-08-10 2018-12-18 Bongiovi Acoustics Llc System and method for digital signal processing
    US10069471B2 (en) 2006-02-07 2018-09-04 Bongiovi Acoustics Llc System and method for digital signal processing
    US10313791B2 (en) 2013-10-22 2019-06-04 Bongiovi Acoustics Llc System and method for digital signal processing
    US9564146B2 (en) 2014-08-01 2017-02-07 Bongiovi Acoustics Llc System and method for digital signal processing in deep diving environment
    US9998832B2 (en) 2015-11-16 2018-06-12 Bongiovi Acoustics Llc Surface acoustic transducer

    Also Published As

    Publication number Publication date
    EP0580579A4 (en) 1994-06-15
    EP0580579A1 (en) 1994-02-02
    DE69129664D1 (en) 1998-07-30
    ES2118093T3 (en) 1998-09-16
    HK1011163A1 (en) 1999-07-02
    WO1992019080A1 (en) 1992-10-29
    DK0580579T3 (en) 1999-04-06
    DE69129664T2 (en) 1998-12-03
    JPH06508445A (en) 1994-09-22
    CA2108696A1 (en) 1992-10-20

    Similar Documents

    Publication Publication Date Title
    EP0580579B1 (en) Noise control apparatus
    US4953655A (en) Acoustic apparatus
    US4628528A (en) Pressure wave transducing
    EP0647343B1 (en) A transducer arrangement for active sound cancellation systems
    EP0724761B1 (en) An active noise cancellation apparatus for a motor vehicle
    KR0158885B1 (en) Loudspeaker system comprising a helmholtz resonator coupled to an acoustic tube
    US4064966A (en) Loudspeaker apparatus
    JPH11220789A (en) Electrical acoustic conversion device
    US5177329A (en) High efficiency low frequency speaker system
    EP0454341A2 (en) An active noise cancellation apparatus
    EP0453230A2 (en) Speaker system
    US5323466A (en) Tandem transducer magnet structure
    EP2077680A1 (en) Loudspeaker system with double chamber enclosure
    EP2043382B1 (en) Sound system
    JPH1094082A (en) Device including sod microphone
    JPH06202673A (en) Silencer device for combustion engine
    CN112901887A (en) Pipeline low-frequency noise control device based on electroacoustic coupling
    KR101956880B1 (en) Earphone Unit with high Band Filter
    JP3086270B2 (en) Speaker box
    Munjal et al. Analysis of a hybrid noise control system for a duct
    JP4218994B2 (en) Method for attenuating sound waves in an environment and structure with controllable acoustic impedance
    JP2924586B2 (en) Secondary sound generator for silencing ducts
    Li et al. Acoustic analysis of coupled loudspeakers for low frequency duct noise reflection
    EP4080906A1 (en) Helmholtz resonators to scale down loudspeaker enclosure size and enhance performance
    JP2009055483A (en) Intercom device

    Legal Events

    Date Code Title Description
    PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

    Free format text: ORIGINAL CODE: 0009012

    17P Request for examination filed

    Effective date: 19931116

    AK Designated contracting states

    Kind code of ref document: A1

    Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

    RHK1 Main classification (correction)

    Ipc: H04R 1/28

    A4 Supplementary search report drawn up and despatched
    AK Designated contracting states

    Kind code of ref document: A4

    Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

    17Q First examination report despatched

    Effective date: 19950705

    GRAG Despatch of communication of intention to grant

    Free format text: ORIGINAL CODE: EPIDOS AGRA

    GRAG Despatch of communication of intention to grant

    Free format text: ORIGINAL CODE: EPIDOS AGRA

    GRAH Despatch of communication of intention to grant a patent

    Free format text: ORIGINAL CODE: EPIDOS IGRA

    GRAH Despatch of communication of intention to grant a patent

    Free format text: ORIGINAL CODE: EPIDOS IGRA

    GRAA (expected) grant

    Free format text: ORIGINAL CODE: 0009210

    AK Designated contracting states

    Kind code of ref document: B1

    Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

    REF Corresponds to:

    Ref document number: 167775

    Country of ref document: AT

    Date of ref document: 19980715

    Kind code of ref document: T

    ITF It: translation for a ep patent filed
    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: EP

    REF Corresponds to:

    Ref document number: 69129664

    Country of ref document: DE

    Date of ref document: 19980730

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: NV

    Representative=s name: ISLER & PEDRAZZINI AG

    REG Reference to a national code

    Ref country code: ES

    Ref legal event code: FG2A

    Ref document number: 2118093

    Country of ref document: ES

    Kind code of ref document: T3

    ET Fr: translation filed
    REG Reference to a national code

    Ref country code: DK

    Ref legal event code: T3

    PLBE No opposition filed within time limit

    Free format text: ORIGINAL CODE: 0009261

    STAA Information on the status of an ep patent application or granted ep patent

    Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

    26N No opposition filed
    REG Reference to a national code

    Ref country code: GB

    Ref legal event code: IF02

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: AT

    Payment date: 20020307

    Year of fee payment: 12

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: DK

    Payment date: 20020312

    Year of fee payment: 12

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: CH

    Payment date: 20020314

    Year of fee payment: 12

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: NL

    Payment date: 20020318

    Year of fee payment: 12

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: LU

    Payment date: 20020319

    Year of fee payment: 12

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: PUE

    Owner name: NCT GROUP, INC. TRANSFER- NEW TRANSDUCERS LIMITED

    Ref country code: CH

    Ref legal event code: PFA

    Free format text: NOISE CANCELLATION TECHNOLOGIES, INC. TRANSFER- NCT GROUP, INC.

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: GR

    Payment date: 20020329

    Year of fee payment: 12

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: BE

    Payment date: 20020417

    Year of fee payment: 12

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: LU

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030419

    Ref country code: AT

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030419

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: CH

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030430

    Ref country code: DK

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030430

    Ref country code: LI

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030430

    Ref country code: BE

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20030430

    REG Reference to a national code

    Ref country code: ES

    Ref legal event code: PC2A

    BERE Be: lapsed

    Owner name: *NOISE CANCELLATION TECHNOLOGIES INC.

    Effective date: 20030430

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: NL

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20031101

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: GR

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20031104

    NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

    Effective date: 20031101

    REG Reference to a national code

    Ref country code: DK

    Ref legal event code: EBP

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: PL

    REG Reference to a national code

    Ref country code: FR

    Ref legal event code: TP

    Ref country code: FR

    Ref legal event code: CD

    Ref country code: FR

    Ref legal event code: CA

    REG Reference to a national code

    Ref country code: GB

    Ref legal event code: 732E

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: IT

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

    Effective date: 20050419

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: FR

    Payment date: 20060313

    Year of fee payment: 16

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: GB

    Payment date: 20060316

    Year of fee payment: 16

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: DE

    Payment date: 20060317

    Year of fee payment: 16

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: ES

    Payment date: 20060405

    Year of fee payment: 16

    GBPC Gb: european patent ceased through non-payment of renewal fee

    Effective date: 20070419

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: DE

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20071101

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: SE

    Payment date: 20060323

    Year of fee payment: 16

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: GB

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20070419

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: IT

    Payment date: 20060430

    Year of fee payment: 16

    PGRI Patent reinstated in contracting state [announced from national office to epo]

    Ref country code: IT

    Effective date: 20080301

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: SE

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20070420

    REG Reference to a national code

    Ref country code: ES

    Ref legal event code: FD2A

    Effective date: 20070420

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: FR

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20070430

    PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

    Ref country code: ES

    Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

    Effective date: 20070420

    PGRI Patent reinstated in contracting state [announced from national office to epo]

    Ref country code: IT

    Effective date: 20080301