WO1992019080A1 - Improvements in and relating to transmission line loudspeakers - Google Patents

Improvements in and relating to transmission line loudspeakers Download PDF

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Publication number
WO1992019080A1
WO1992019080A1 PCT/US1991/002731 US9102731W WO9219080A1 WO 1992019080 A1 WO1992019080 A1 WO 1992019080A1 US 9102731 W US9102731 W US 9102731W WO 9219080 A1 WO9219080 A1 WO 9219080A1
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WIPO (PCT)
Prior art keywords
drain
back chamber
chamber
loudspeaker
transmission line
Prior art date
Application number
PCT/US1991/002731
Other languages
French (fr)
Inventor
Khosrow Eghtesadi
William John Joseph Hoge
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 CA002108696A priority Critical patent/CA2108696A1/en
Priority to DK91920600T priority patent/DK0580579T3/en
Priority to PCT/US1991/002731 priority patent/WO1992019080A1/en
Priority to EP91920600A priority patent/EP0580579B1/en
Priority to DE69129664T priority patent/DE69129664T2/en
Priority to ES91920600T priority patent/ES2118093T3/en
Priority to JP3518527A priority patent/JPH06508445A/en
Publication of WO1992019080A1 publication Critical patent/WO1992019080A1/en
Priority to HK98112067A priority patent/HK1011163A1/en

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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 a method of and apparatus for improving the performance of transmission line loudspeakers and has particular applications in active noise control, high fidelity audio, and sound reinforcement systems.
  • the simplest form of a loudspeaker system is the direct radiator.
  • a loudspeaker radiates sound directly form 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.
  • This invention relates to 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 drive 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 trough 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 used 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.
  • 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.
  • the transmission line should be a horn.
  • a compact system might use a short tube. Such a tube is too short to exhibit transmission line characteristics. It will act as lumped parameter acoustic mass instead.
  • the transmission characteristics of the improved 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.
  • Another arrangement of the apparatus according to the present invention 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 exists 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 wavelenghts which are long compared to the size of the outlet.
  • 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 simplfied 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 analagous circuit.
  • 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 fornt chamber of the enclosure 3.
  • the sound form 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 electroydnamic 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 Bl of the motor causes a driving force.
  • the sum of this force and the various reaction forces in the system gives in the total force driving the diaphragm F D .
  • This force accelerates the diaphrgam 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 .
  • the front side pushes against the surrounding air and a flow into the front chamber 3 results.
  • This volume 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 from 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 presurizes 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 another component of F D is another component of F D .
  • the analysis of the system is similar, except that the line impedance is simplifed 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 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 7 and the connection to the noisy duct 8.
  • a long, narrow tube 9 allows outsider 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” cause a low pressure region which "draws" the outside air. This air may be useful for cooling or removal of corrosive gases.
  • VBBP Vented Box Bandpass Loudspeaker
  • Fig. 11 shows the simplified acoustical analagous circuit of the Vented Box Bandpass Loudspeaker (VBBP) configuration.
  • the terms R o and P g are determined by the following formulal:
  • Equation (1) Substitute Equations (4) and (6) into the Equation (1)

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  • 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)

Abstract

The sound wave radiated from the front surface (UF) of a loudspeaker driver diaphragm is of opposite polarity with respect to that radiated from the back surface (UB). If the two signals are directly combined, they will tend to cancel one another. An acoustic phase inversion network (5) is used to ensure that the backwave is in phase with the front wave, and the combined signals are used to drive the inlet of a loudspeaker transmission line (6).

Description

improvements In and Relating to Transmission Line Loudspeakers
BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates to a method of and apparatus for improving the performance of transmission line loudspeakers and has particular applications in active noise control, high fidelity audio, and sound reinforcement systems.
2. Discussion of the Relevant Art.
The simplest form of a loudspeaker system is the direct radiator. Such a loudspeaker radiates sound directly form 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.
SUMMARY OF THE INVENTION
This invention relates to 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 drive 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 trough 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 used 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.
In one arrangement of the apparatus according to the present invention 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 should be a horn. However, a compact system might use a short tube. Such a tube is too short to exhibit transmission line characteristics. It will act as lumped parameter acoustic mass instead.
The transmission characteristics of the improved 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. Another arrangement of the apparatus according to the present invention 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 exists 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 wavelenghts which are long compared to the size of the outlet.
Another arrangement of the apparatus according to the current invention which also has particular application in active noise cancellation systems is similar to that described immediately above. However, in this arrangmeent 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:
BRIEF DESCRIPTION OF THE DRAWINGS
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 simplfied 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 analagous circuit.
Description of the Preferred Embodiments
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 fornt chamber of the enclosure 3. The sound form 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 electroydnamic 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 Bl of the motor causes a driving force. The sum of this force and the various reaction forces in the system gives in the total force driving the diaphragm FD. This force accelerates the diaphrgam 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 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 from 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 presurizes 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 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 from 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 pp. 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 simplifed 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 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 7 and the connection to the noisy duct 8. A long, narrow tube 9 allows outsider 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" cause 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 symbol used in Figures 10 and 11 and in the calculations are: 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
1 lenght 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
Free Air Resonance frequency
Figure imgf000009_0001
QES Electro-Magnetic Q at fs
Qms Mechanical Q at fs Qts Total Q at
Figure imgf000009_0002
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 analagous circuit of the Vented Box Bandpass Loudspeaker (VBBP) configuration. The terms Ro and Pg are determined by the following formulal:
Figure imgf000010_0001
In the following circuit analysis, assumptions are made that there is a lossless enclosure (internal box resistance =
O and leakage resistance =α) and that the voice coil inductance is small (LF≈O)
The circuit analysis is as follows:
Figure imgf000010_0002
Figure imgf000010_0003
Figure imgf000010_0004
(4) From Equation (2 ) UF= (1+S2MAPCAP) Uo US+UAB=UF
(5) US=UF-UAB
From equation
Figure imgf000010_0005
Figure imgf000011_0001
Substitute Equations (4) and (6) into the Equation (1)
Figure imgf000011_0002
(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
Figure imgf000012_0001
Figure imgf000013_0001

Claims

1. Apparatus for achieving improved performance of a
transmission line loudspeaker producing a front and back wave comprising one or more electromagnetic driver means mounted in an enclosure means having front and back chamber means connected by a conduit means so that the back wave of the loudspeaker is constructively summed with the front wave in the front chamber means, and a transmission line means attached to the front chamber means comprising the only sound outlet of the system.
2. Apparatus as claimed in claim 1, in which the transmission line means is a short tube means in the enclosure configured to produce a desired band-pass frequency response characteristic.
3. Apparatus as claimed in claim 2, in which a separate pipe means passes through the loudspeaker enclosure means and exits through the short take means for the purpose of noise cancellation.
4. Apparatus as claimed in claim 1, in which a drain means is added between the from and back chamber means to allow trapped liquids to drain from the back chamber.
5. Apparatus as claimed in claim 2, in which a drain tube means is added between the front and back chamber means to allow trapped liquids to drain from the back chamber.
6. Apparatus as claimed in claim 3, in which a drain hole is provided between the front and back chamber means to allow trapped liquids to drain from the back chamber.
7. Apparatus as claimed in claim 2, including a noisy duct means to which the short tube means is connected for the purpose of noise control.
8. Apparatus as claimed in claim 7, in which the short tube means is formed by the area between a plate means in the front chamber means and the connection to the noisy duct or pipe.
9. Apparatus as claimed in claim 7, in which a ventilation tube means is connected between either the front or the back chamber means and the outside air and a venturi-like structure means is in the noisy duct means in order to create a low pressure region to draw outside air through the system.
10. Apparatus as claimed in claim 1 in which said conduit means comprises a hole connecting said front and back chambers.
11. Apparatus for achieving improved performance of a transmission line loudspeaker means producing a front and back wave comprising a driver means, said driver means mounted in an enclosure means, said enclosure means having front and back chamber means connected by a conduit means so that the back wave of the loudspeaker means is constructively summed with the means attached to the from chamber means comprising the sole sound outlet of the system.
12. Apparatus as claimed in claim 11 in which the transmission line means is a short tube means in the enclosure configured to produce a desired band-pass frequency response characteristic.
13. Apparatus as claimed in claim 2, in which a separate pipe means passes through the loudspeaker enclosure means and exits through the short tube means for the purpose of noise cancellation.
14. Apparatus as claimed in claim 1, in which a drain means is added between the front and back chamber means to allow trapped liquids to drain from the back chamber.
15. Apparatus as claimed in claim 2, in which a drain tube means is added between the from and back chamber means to allow trapped liquids to drain from the back chamber.
16. Apparatus as claimed in claim 3, in which a drain hole is provided between the front and back chamber means to allow trapped liquids to drain from the back chamber.
17. Apparatus as claimed in claim 2, including a noisy duct means to which the short tube means is connected for the purpose of noise control.
18. Apparatus as claimed in claim 7, in which the short tube means is formed by the area between a plate means in the front chamber means and the connection to the noisy duct or pipe.
19. Apparatus as claimed in claim 7, in which a ventilation tube means is connected between either the front or the back chamber means and the outside are and a venturi-like structure means is in the noisy duct means in order to create a low pressure region to draw outside air through the system.
PCT/US1991/002731 1991-04-19 1991-04-19 Improvements in and relating to transmission line loudspeakers WO1992019080A1 (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
CA002108696A CA2108696A1 (en) 1991-04-19 1991-04-19 Improvements in and relating to transmission line loudspeakers
DK91920600T DK0580579T3 (en) 1991-04-19 1991-04-19 Noise Control Device
PCT/US1991/002731 WO1992019080A1 (en) 1991-04-19 1991-04-19 Improvements in and relating to transmission line loudspeakers
EP91920600A EP0580579B1 (en) 1991-04-19 1991-04-19 Noise control apparatus
DE69129664T DE69129664T2 (en) 1991-04-19 1991-04-19 DEVICE FOR NOISE REDUCTION
ES91920600T ES2118093T3 (en) 1991-04-19 1991-04-19 NOISE CONTROL DEVICE.
JP3518527A JPH06508445A (en) 1991-04-19 1991-04-19 Improvements regarding transmission pipe loudspeakers
HK98112067A HK1011163A1 (en) 1991-04-19 1998-11-17 Noise controller apparatus

Applications Claiming Priority (2)

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

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WO1992019080A1 true WO1992019080A1 (en) 1992-10-29

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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)

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EP0828466A1 (en) * 1994-05-10 1998-03-18 Noise Cancellation Technologies, Inc. Active noise cancelling muffler
EP1323332A1 (en) * 2000-10-06 2003-07-02 Logitech Europe S.A. Dual-chamber loudspeaker
EP1994793A2 (en) * 2006-03-15 2008-11-26 Thomas J. Danley Sound reproduction with improved low frequency characteristics
EP2581567A1 (en) * 2011-10-14 2013-04-17 J. Eberspächer GmbH & Co. KG Active acoustic baffler
US9564146B2 (en) 2014-08-01 2017-02-07 Bongiovi Acoustics Llc System and method for digital signal processing in deep diving environment
US9615813B2 (en) 2014-04-16 2017-04-11 Bongiovi Acoustics Llc. Device for wide-band auscultation
US9621994B1 (en) 2015-11-16 2017-04-11 Bongiovi Acoustics Llc Surface acoustic transducer
US9638672B2 (en) 2015-03-06 2017-05-02 Bongiovi Acoustics Llc System and method for acquiring acoustic information from a resonating body
US9741355B2 (en) 2013-06-12 2017-08-22 Bongiovi Acoustics Llc System and method for narrow bandwidth digital signal processing
US9793872B2 (en) 2006-02-07 2017-10-17 Bongiovi Acoustics Llc System and method for digital signal processing
EP3162084A4 (en) * 2014-06-26 2017-12-13 Bisset, Anthony Allen A compact wideband bass and midrange horn-loaded speaker system
US9883318B2 (en) 2013-06-12 2018-01-30 Bongiovi Acoustics Llc System and method for stereo field enhancement in two-channel audio systems
US9906867B2 (en) 2015-11-16 2018-02-27 Bongiovi Acoustics Llc Surface acoustic transducer
US9906858B2 (en) 2013-10-22 2018-02-27 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
US10158337B2 (en) 2004-08-10 2018-12-18 Bongiovi Acoustics Llc System and method for digital signal processing
US10639000B2 (en) 2014-04-16 2020-05-05 Bongiovi Acoustics Llc Device for wide-band auscultation
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
US10820883B2 (en) 2014-04-16 2020-11-03 Bongiovi Acoustics Llc Noise reduction assembly for auscultation of a body
US10848867B2 (en) 2006-02-07 2020-11-24 Bongiovi Acoustics Llc System and method for digital signal processing
US10848118B2 (en) 2004-08-10 2020-11-24 Bongiovi Acoustics Llc System and method for digital signal processing
US10959035B2 (en) 2018-08-02 2021-03-23 Bongiovi Acoustics Llc System, method, and apparatus for generating and digitally processing a head related audio transfer function
CN113504663A (en) * 2021-07-23 2021-10-15 歌尔光学科技有限公司 Sound production module, sound elimination method of sound production module and intelligent glasses
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
US11211043B2 (en) 2018-04-11 2021-12-28 Bongiovi Acoustics Llc Audio enhanced hearing protection system
US11431312B2 (en) 2004-08-10 2022-08-30 Bongiovi Acoustics Llc System and method for digital signal processing

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Cited By (40)

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EP0828466A4 (en) * 1994-05-10 1998-03-18
EP0828466A1 (en) * 1994-05-10 1998-03-18 Noise Cancellation Technologies, Inc. Active noise cancelling muffler
EP1323332A1 (en) * 2000-10-06 2003-07-02 Logitech Europe S.A. Dual-chamber loudspeaker
EP1323332A4 (en) * 2000-10-06 2006-01-25 Logitech Europ Sa Dual-chamber loudspeaker
US11431312B2 (en) 2004-08-10 2022-08-30 Bongiovi Acoustics Llc System and method for digital signal processing
US10666216B2 (en) 2004-08-10 2020-05-26 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
US10848118B2 (en) 2004-08-10 2020-11-24 Bongiovi Acoustics Llc System and method for digital signal processing
US11425499B2 (en) 2006-02-07 2022-08-23 Bongiovi Acoustics Llc System and method for digital signal processing
US10848867B2 (en) 2006-02-07 2020-11-24 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
US10069471B2 (en) 2006-02-07 2018-09-04 Bongiovi Acoustics Llc System and method for digital signal processing
US9793872B2 (en) 2006-02-07 2017-10-17 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
EP1994793A2 (en) * 2006-03-15 2008-11-26 Thomas J. Danley Sound reproduction with improved low frequency characteristics
EP1994793A4 (en) * 2006-03-15 2011-11-02 Thomas J Danley Sound reproduction with improved low frequency characteristics
CN103114889A (en) * 2011-10-14 2013-05-22 J·埃贝斯佩歇合资公司 Active sound absorbers
EP2581567A1 (en) * 2011-10-14 2013-04-17 J. Eberspächer GmbH & Co. KG Active acoustic baffler
US9206717B2 (en) 2011-10-14 2015-12-08 Eberspaecher Exhaust Technology Gmbh & Co. Kg Active sound absorbers
US9883318B2 (en) 2013-06-12 2018-01-30 Bongiovi Acoustics Llc System and method for stereo field enhancement in two-channel audio systems
US9741355B2 (en) 2013-06-12 2017-08-22 Bongiovi Acoustics Llc System and method for narrow bandwidth digital signal processing
US10999695B2 (en) 2013-06-12 2021-05-04 Bongiovi Acoustics Llc System and method for stereo field enhancement in two channel audio systems
US10412533B2 (en) 2013-06-12 2019-09-10 Bongiovi Acoustics Llc System and method for stereo field enhancement in two-channel audio systems
US10917722B2 (en) 2013-10-22 2021-02-09 Bongiovi Acoustics, Llc System and method for digital signal processing
US9906858B2 (en) 2013-10-22 2018-02-27 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
US11418881B2 (en) 2013-10-22 2022-08-16 Bongiovi Acoustics Llc System and method for digital signal processing
US11284854B2 (en) 2014-04-16 2022-03-29 Bongiovi Acoustics Llc Noise reduction assembly for auscultation of a body
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
EP3162084A4 (en) * 2014-06-26 2017-12-13 Bisset, Anthony Allen A compact wideband bass and midrange horn-loaded speaker system
US9564146B2 (en) 2014-08-01 2017-02-07 Bongiovi Acoustics Llc System and method for digital signal processing in deep diving environment
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
US9621994B1 (en) 2015-11-16 2017-04-11 Bongiovi Acoustics Llc Surface acoustic transducer
US9998832B2 (en) 2015-11-16 2018-06-12 Bongiovi Acoustics Llc Surface acoustic transducer
US11211043B2 (en) 2018-04-11 2021-12-28 Bongiovi Acoustics Llc Audio enhanced hearing protection system
US10959035B2 (en) 2018-08-02 2021-03-23 Bongiovi Acoustics Llc System, method, and apparatus for generating and digitally processing a head related audio transfer function
CN113504663A (en) * 2021-07-23 2021-10-15 歌尔光学科技有限公司 Sound production module, sound elimination method of sound production module and intelligent glasses

Also Published As

Publication number Publication date
EP0580579A1 (en) 1994-02-02
DE69129664D1 (en) 1998-07-30
HK1011163A1 (en) 1999-07-02
EP0580579A4 (en) 1994-06-15
DK0580579T3 (en) 1999-04-06
ES2118093T3 (en) 1998-09-16
JPH06508445A (en) 1994-09-22
EP0580579B1 (en) 1998-06-24
DE69129664T2 (en) 1998-12-03
CA2108696A1 (en) 1992-10-20

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