JPH0450683A - Window for acoustic type and manufacture thereof - Google Patents

Abstract

PURPOSE: To obtain a drastically sharp waveform having no attenuation nor deformation while ensuring a desired structural strength by a structure wherein a pair of structural barrier walls form a window passing a desired sound waveform by laminating a core. CONSTITUTION: Barrier walls 12, 14 are laminated on a core 16. A specific technology for forming a laminate coupling between the core 16 and the barrier walls 12, 14 is selected from the view point of the chemical characteristics of a specific material for forming the barrier walls 12, 14 and the core 16. The structural characteristics in the formation of a window 10 are regulated depending on the thickness, the tensile modulus of elasticity and the compression modulus of elasticity of barrier wall, and the thickness and modulus of rigidity of the core.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The invention relates to windows for the passage of desired sound waveforms, and more particularly to windows for the passage of desired sound waves, such as those used under submerged liquid action, e.g. Regarding windows. More particularly, the present invention relates to sonar windows, such as domes for use on surfaces in both military and commercial applications and on submersible ships.

[Background of the invention]

Sonic windows, such as sonar domes for use in transmitting or receiving acoustic waves in liquid environments, are known. Traditionally, these windows have been constructed from a single thickness of wire, optionally coated with a metal, e.g., a bioactive material, e.g., rubber containing a biocide to inhibit biocontamination of the window surface. It's here.

Typically, such windows on the exterior surface are free-liquid,
For example facing the body of an ocean, lake or tank. Such windows on the inner surface at least partially define a chamber conventionally filled with water or other liquid. Such a window is so acoustically "sharp" as to produce the desired low deformation and attenuation of the sound wave energy passing through the window as well as the desired low change in angle characterized by the impingement of the sound wave energy against the window. Substantial effort has been devoted to shaping.

Such windows are subject to certain undesirable characteristics.

For example, windows manufactured from hard materials, such as steel, generate significant amounts of acoustic noise associated with the passage of water over the window, and vibrations associated with the operation of machinery carried on the ship in which the window is contained. A significant amount of sound noise arising from frequencies can be transmitted through. Additionally, these relatively rigid windows can create significant bouncing or reflection effects due to the sound wave energy impinging on the window surface.

Such bounces can result in a substantial reduction in the signal transmitted through the window, and during the transmission of a sound wave form from within the chamber confined by the window, if reflections occur from the inner surface of the window, the echo False or false decisions and/or productions result.

Alternative materials to steel or other metals used in dome fabrication have been proposed. Fiber reinforced plastics (FRP) have been proposed as suitable window materials.

Such FRP materials exhibit higher corrosion resistance than rope, but - for boat fishing - have many of the same characteristic difficulties as steel with respect to sound clarity, attenuation and reflection characteristics.

Windows, such as sonar domes, have a frequency of about 500Hz to about 500Hz.
Transmission of sound energy having a frequency of KHz is required. These frequencies are approximately 0.003m underwater.
This corresponds to a wavelength of about 3 m, and this wavelength is subject to some variation depending on the material through which the waveform is transmitted.

For conventional domes of metal or reinforced plastic, if the thickness of the material into which the dome is fabricated deviates substantially by 172 wavelengths of the sound frequency transmitted through the dome, the reduction through insertion loss, i.e., 201ogPo/Pt
(where PO is the wave incident pressure and pt is the transmitted pressure) is no longer acceptable. The sonar dome should be structurally configured to withstand certain structural loads. This configuration provides an inherent thickness of structural material. If this thickness deviates from the 1/2 wavelength that is transmitted, then effective indiscretion for a given acoustic waveform frequency can result in a simple reduction in the waveform energy that is transmitted through the thickness of the material.

By nature, sonar domes are not manufactured from the sole use of acoustically vivid materials; sometimes it is desired that the sonic energy be transmitted through windows or coated openings in the hull. The same constraints that affect the performance of conventional sonar domes can also affect the acoustic performance of such windows.

The structural features in forming the sonar dome and windows are made of high modulus material, i.e., at least about 100
,000 psi (6,895 x 105 KPa) or more and more preferably about 1,000,000 psi (6,89
Traditionally, the focus has been on materials selected from those having a Young's modulus of 5 x 10" x Pa) or higher. These materials exhibit elongation at break characteristics approaching zero and are used for the desired thin adjustable windows. The use of such hard, high strength materials makes it extremely difficult to sub-adjust sonar domes and windows formed from such materials. There was a tendency.

The properties of the material of the structure for such a sonar dome or window, taken together with the structural loads imposed on the dome and window, leave much to be desired for adjustment of properties such as clarity, reduction and similar There has been a tendency to establish the sonic properties of sonar domes without flexibility.

A sonar dome or window that can be adjusted to substantially reduce the frequency of sound waves for passage through the sonar dome or window has substantial applications in the military and commercial fields. Similarly, domes or windows formed of one or more materials configured to reduce the darkness of the passage of acoustic signals therethrough, reflected signals may be utilized.

Similarly, structures for sonar domes and windows with enhanced self-braking properties can be created, for example by passage of water along the sonar dome or window or by machinery aboard a ship that includes the sonar dome or window. and can be used substantially to reduce noise and other signals due to vibrations generated by transmitted vibrations of the device.

[Summary of the invention]

The present invention provides a window for the passage of the desired sound waveform in which a pair of structural partitions laminate the core. The septum is made of a material selected from the group consisting of: i) reinforced and unreinforced thermoset plastics and thermoplastics; ii) low density, high modulus metals, metal alloys, and iii) carbon composites. formed from.

The core has a pressure of about 200 psi (138 KPa) to
Static shear modulus of approximately 15,000 psi (10,34X10'KPa) and approximately 600 ps 1 (415XF'a)
~ Approximately 50,000psi (34,475X10'KP
It is formed from a material having a Young's modulus of a). The core material has an elongation at break of at least about 3% and an elongation at break of at least about 1.
There exists a longitudinal velocity growth characteristic for transmitted sound frequencies of 200 to about 2,000 m/s. The septum and core together define a thickness of approximately 1/2λ±25% for the desired sound waveform to be transmitted through the window.

Suitable sonar windows of the present invention include: 1) reinforced and unreinforced thermosets and thermoplastics; i
i) low density, high modulus metals and metal alloys and ni)
about 0.001 by providing a pair of partition walls formed from a material selected from the group consisting of carbon composite materials.
m to about 1.5 m to pass a sound waveform with a desired λ through the window.

The core is laminated between the partition walls and approximately 200 ps 1
(138KPa) to approximately 15,000psi (10,3
static shear modulus of 4 x 10' KPa) and approximately 600 psi
(415KPa) ~ Approx. 50,000ps 1 (34,000ps)
475 x 10'KPa). The core material has an elongation at break of at least about 3% and an elongation at break of about 1.
It has a longitudinal velocity growth characteristic for transmitted sound frequencies of 200 to about 2,000 m/s.

Desirably, the septum and core are shaped together as a laminate to provide exactly 172 mm of the desired acoustic waveform thickness to be transmitted. The bulkhead and core laminate is then formed into the desired physical shape of the window, such as a bow dome or other curved shape for the desired match with the hull of a ship or submarine.

The core is preferably formed from natural or synthetic rubber, other elastomer, or reciprocable, interstitial or unfilled synthetic polymer having the desired physical and dynamic properties. The septum is typically formed from steel, titanium, aluminum, copper, nickel and alloys thereof, fiber-reinforced thermosets or thermoplastics, or carbon composites.

[Best mode of the invention] The present invention provides a window for the passage of sound waves.

The windows of the present invention have desirable enhanced damping and self-damping properties.

A window 10 of the present invention is shown in FIG. The window 10 consists of partition walls 12, 14 and a core 16. Window 10 in Figure 1
is shown in cross-section and is a representative cross-section of an embodiment sonar bow dome as it relates to a submarine or ship.

The window 10 is shaped to separate the acoustic transmitting or receiving device (not shown) from the open liquid (fresh or salt water) through which the desired acoustic signal is transmitted or received. Such arcuate domes may have any suitable or conventional shape, such as generally elliptical, hyperbolic, circular, and similar shapes. On the other hand, the sound wave window 1
0 can be simply formed on the curved part of the hull surface,
and thereby relatively similar in appearance to some window installations in buildings and other terrestrial structures. The particular physical form taken by the window 10 of the present invention is determined by the particular physical form provided by a sonic transmission or passive device located behind the window or within an enclosure at least partially defined by the window 10. It would be a function of sound wave transmission/passive function.

In the window 10 of the present invention, the partition walls 12, 14 are formed from any suitable or conventional construction material. This material can be a reinforced or unreinforced thermoset or thermoplastic. These partition walls 12, 14, on the other hand, may be formed from a high density, high modulus metal or metal alloy. On the other hand, septum 1214 may be formed from a carbon composite material.

The selection of specific materials for the construction of partition walls 12, 14 is
It is a function of the structural suitability and sound clarity properties required of the resulting window 10 and the freedom from sound distortion associated with the particular bulkhead material used.

Compatible reinforced plastics and especially so-called fiber reinforced plastics (FRP) are preferred in the practice of the invention. Filter reinforcements can include glass beads or spheres, carbon granules, carbon or graphite fibers, and other suitable or conventional filler materials. Most preferably, glass fiber reinforced plastics are used in the practice of this invention.

Such reinforced plastics are well known in the art, and any suitable or conventional such fiber reinforced plastic may be used. Relatively high strength per unit weight is often associated with FRP plastics made with thermoset resins, such as epoxies or furans, and these thermoset FRP plastics are preferred in the practice of the present invention. However, thermoplastic materials such as polyether ether (PEEKe
) is expected to be increasingly useful in forming the structures of the present invention. Other thermoplastic resins utilized in the practice of this invention include polyethylene, polypropylene, vinyl chloride, chlorinated vinyl chloride, acrylonitrile-butadiene styrene copolymer, polyvinylidine furiolide, polytetrafluoroethylene, polycarbonate and other suitable or conventional thermoplastic resins.

On the other hand, the partition walls 12 and 14 may be formed from metal.

The metal is preferably a low density, relatively high modulus metal or metal alloy. Steel, titanium, aluminum, copper, stainless steel, magnesium, biryllium, nickel and suitable alloys of these metals are particularly preferred in the practice of this invention.

Low density generally means a density of about 9 g/cd or less. High modulus is generally at least about 5 x 10'psi (34,475 x 106 KP
a) means the elastic modulus.

Furthermore, the partition walls 12, 14 may be formed from a carbon composite material. The carbon can be present in graphite or non-oriented (basic) carbon form, and the composite material can be formed in any suitable or conventional well-known manner. 1
One composite form is developed by laying up pre-bragged carbon fabrics; and another composite form is developed by using fiber-resin blends. Both are then burned to produce carbon.

Well known methods and techniques, such as densification with carbon vapor infiltration or resin impregnation methods, can be used to strengthen and compact such carbon composite structures.

The materials selected for manufacturing the septum 12, 14 of the present invention are such that the thickness of the septum used will support the expected stresses and strains on the window 10 associated with operation in a submerged environment. It should have sufficient shear stiffness.

Core 16 is approximately 200 ps i (1,380 KPa
) ~ Approximately 15,000psi (103,500KPa)
static shear modulus of about 600 ps i (4,140K
Pa) ~ approx. 50,000psi (344,750K
It is formed from a material having a Young's modulus of Pa). The core material has an elongation at break of at least about 3% and an elongation at break of about 1%.
, 200 to about 2.000 m7 seconds, for the acoustic waveform transmitted through the window 10.

The term static shear modulus means a weak modulus in shear or a measure of the resistance of a material to shear stress and is equal to the shear stress divided by the resulting angle of deformation in radius. Static shear modulus is also known as stiffness modulus, stiffness modulus or shear stress.

As used herein, Young's modulus refers to the ratio of the simple tensile stress applied to a material to the resulting stress equivalent to the tensile force. Young's modulus is also a measure of elastic modulus for materials, where elastic modulus is also known as elastic modulus, elastic modulus or elastic modulus modulus.

The core 16 preferably has a longitudinal velocity growth characteristic for the acoustic waves passed through the core 16 that is very close to or below the velocity growth of the liquid medium with which the window is impregnated. As illustrated, when the medium liquid is water, its longitudinal velocity growth is preferably about 1,200 to 2,000 m/
Seconds.

Typically, the core is formed from natural or synthetic rubber or other elastomer, but may also be formed from castable filled or unfilled synthetic polymers. Synthetic rubbers suitable for use in the present invention include styrene-butadiene and acrylonitrile-based rubbers, the latter commonly known in the art as nitrile rubbers. Chlorinated rubbers, such as NEOPRENE@, are also utilized in forming the core 16.

Other elastomers used in the practice of this invention include polyurethane, polybutadiene and acrylic-copolymer rubbers and EPDMS (ethylene propylene-based polymer). "Rubber" means vulcanized or crosslinked rubber made according to any suitable or conventional technique. “
By elastomer° is meant a material that has the ability to recover, at least in part, to its previous profile or shape upon removal of a profile or shape-deforming force.

The castable polymer can be filled using any suitable or conventional material. As shown, carbon black or glass fibers can be used as fillers. Castable filled or unfilled synthetic polymers suitable for use in the practice of this invention include polyurethanes and so-called reactive liquid polymers such as B, F, Goodric as HYCARe.
h Company.

The rubbers and elastomers used in the practice of the present invention to form core 16 can include fillers. The filler may be from 0 to 100 parts by weight of elastomer or rubber.
present in an amount of about 50 parts by weight, and - for boat fishing, in an amount of about 15 to 40 parts by weight per 100 parts by weight of elastomer or rubber. Fillers can be particulates, such as carbon black, glass microspheres or microbeads, or additives such as fibers, such as minerals, polyesters, polyolefins, polyaramids, polyamides and polyvinyls, such as polyvinyl alcohol (1 m/6 denier).
It can be. Use of a commercially available carbon black, KETJENe, on natural rubber at 40 parts by weight of carbon black per 100 parts by weight of natural rubber produces a core 16 with a Young's modulus of 2,400 psi. K to the same natural rubber
The use of 20 parts by weight of ETJEN black (also 1 mm
/6 denier polyvinyl alcohol may also be used), 8,000 (5,516 x 10'KPa)
) ~12,000 (8,274X10'KPa) ps
A core material 16 having a Young's modulus of i is manufactured. For the rubber or elastomer used to form the core 16, any suitable or conventional filler material may be used, but the longitudinal velocity growth characteristics for the desired sonic shape of the resulting core 16 will be appreciated. A particular filler material is selected that provides the desired elastic modulus, static shear modulus, and Young's modulus to provide any core 16 with the desired elastic modulus, static shear modulus, and Young's modulus.

Other suitable or conventional materials may provide core 16 with constraints on static shear modulus, Young's modulus, elongation at break, and longitudinal velocity growth characteristics for acoustic waves through the material that meet the criteria set forth herein. It should be understood that it can be used to form.

Preferably, the core material is about 3,000 ps i
(20,685KPa) to approximately 15,000psi (10
3,433 KPa) static shear modulus, approximately 1,000 ps
i (6B, 950KPa) ~ approx. 50,000psi (
344,750 KPa) and a Young's modulus of at least about 6
% elongation at break.

Preferably, the material also has at least 0
．． have a loss tangent or dynamic loss ratio of 0.05 or greater. This loss tangent is the ratio of the viscous modulus to the elastic modulus for the material. By viscous modulus is meant a modulus that is not recovered or preserved and is proportional to the deformation force that is observed only under dynamic stress.

Modulus of elasticity means the ratio of an increment of a particular form of stress to an increment of a certain form of strain, and is also known as the modulus of elasticity.

These elastic and viscous moduli are hereinafter referred to as dynamic moduli.

Core 16 with these favorable static and dynamic properties
The use of a conventional sonar window produces a window with enhanced critical damping properties that can function to reduce interference with inherent noise signals.

Such noise can be created by vibrations established within the window 1O by transmitted sound waveforms resulting from the operation of mechanical equipment onboard ships using such windows. On the other hand, the flow type of fluid (through which the window moves during any vessel motion with which the window is associated) transmits acoustic waves at frequencies that are detrimental to the transmission and reception of acoustic signals through the window 10. Window 10 that can cause the generation of shapes
vibration modes can be generated in the structure. While older windows, such as those formed by FRP, exhibit typical critical attenuation factors of about 0.5%, the window 10, such as the embodiment dome shown in cross-section in FIG. Specifically, it shows a critical damping rate of 2% to 3%.

Another preferred embodiment of the invention is shown in FIG.

In FIG. 2, the same structural parts as in FIG. 1 are designated by reference numerals. With respect to FIG. 2, window 10 is shown having septum 12, 14 and core 16. core 1
The septa on the surfaces not in contact with 6 are coated with a coating or layer 18, 20 of synthetic or natural rubber or other elastomer. The coating is approximately 1716 inches (0,16 cm)
~1 inch (2,54 CI+) thick. The elastomer preferably includes a suitable or conventional biologically active agent configured to inhibit the formation of biological contaminants on the layers 18,20. Traditional biofouling inhibition compounds are
well known. Suitable synthetic rubbers used to form layer 1820 include N0FOUL® B, F,
Obtained from Goodrich Company.

In the embodiments of FIGS. 1 and 2, the partition walls 12 and 14 are laminated to the core 16. Core 16 and bulkhead 12
, 14, lamination fixation may be achieved using adhesive techniques or polymeric crosslinking techniques such as vulcanization or other chemical crosslinking. Core 16 and bulkhead 1
The particular technique for forming the laminated bond between the bulkheads 12 , 14 is typically selected in view of the chemistry of the particular materials forming the septa 12 , 14 and the core 16 . It is important that the septum 12, 14 and the core 16 exist in laminated contact for the transmission of sound waves across the septum-core interface to avoid distortion of the transmitted sound waveform and signal attenuation. be. Similarly, coating or layer 18
, 20 are applied to the septum 12, 14 using gluing, vulcanization, other crosslinking techniques, or other suitable or conventional techniques.

Such techniques are known in the art.

The thickness of the window as shown in either figure 1 or 2 is
It is a function of the structural strains and stresses to which the window must withstand and the wave number or wavelength of the sound waveform passed through the window 10 for transmission or reception. The window measured from the outer surface of one septum 12 to the outer surface of the other septum 14 is approximately 172±25 of the wavelength of the sound wave passing through that window.
% sound thickness is desired. More preferably, the thickness of this sound is ±15%. core 16
The thickness can be adjusted to provide the desired 1/2-wave thickness. Adjustment of the core thickness is also assisted through appropriate selection of specific materials to form a core with the desired enhanced or reduced longitudinal velocity growth characterized by the acoustic waveform passed through the core. obtain. Typically, core materials with low longitudinal velocity growth characteristics may be made thinner than core materials with more undulating longitudinal velocity growth characteristics.

The effect of adjusting the combined acoustic thickness of the bulkhead and core in the window 10 of the present invention on the thickness of the 1/2-wave is shown in FIG. FIG. 3 is a representative graph of attenuation loss (decibels) as a function of frequency (Hz). Curves 22 and 24 show the acoustic performance of windows 10 formed from the same septum thickness and material. Curve 24 shows a window 10 having a core 16 that is thinner than the core shown by curve 22 by a factor of about two.

Curve 24 shows excellent efficacy characteristics as measured by a low signal due to the thin core 16, but surprisingly, the thin core does not work well against such reductions at low frequencies.

Therefore, if accurate transmission of a particular frequency across window 10 is desired, the thickness and material of the septum and core combination are selected and adjusted to provide the desired low signal reduction. obtain.

It is important to note that the window 10 shown by curve 24 is less rigid in terms of bending than the window shown by curve 22.

FIG. 4 is a representative graph of signal decline plotted as a function of frequency (H2). The curve 26 is a 1-1/4 inch homogeneous glass reinforced plastic (G
Figure 3 shows the signal-reducing efficacy characteristics of windows formed from PR). The polymer binder used to form the glass reinforced plastic was an epoxy that cured at 121°C. Conversely, curve 28 represents a glass-reinforced polymer septum 12.14 formed of the same glass-reinforced polymer as the window represented by curve 26, except that the respective
is 0.5 inches (1,27C11) thick and the core formed from natural rubber is 2.5 inches (6,
35C11)] for a window structure of the present invention.

The performance shown by curve 28 is at 1/2-wave frequency 30
shows minimal local signal reduction at , and 1/4-
The maximum local signal drop is shown at wave frequency 32. Conversely, conventional GRP as shown by curve 26
The window shows a steadily increasing signal decline as a function of frequency. Like other conventional windows, the C,RP window shown by curve 26, unlike the window of the present invention, has significantly less "adjustment".
° cannot.

The presence or absence of coating layers 18, 20 as shown in FIG. 2 does not appear to substantially affect the performance of the window 10 of the present invention. The acoustic performance of the window of the present invention is determined by the partition wall 1
2 , 14 and the thickness of the core 16 and other physical parameters and related to the materials selected to form these elements 12 , 14 , 16 significantly influenced by longitudinal velocity growth characteristics. The magnitude of any transmission loss through the partition walls 12, 1.4 and the core 16 is
and by the density, thickness and longitudinal velocity growth characteristics of the core 16 and by the longitudinal dynamic loss rate of the core. This longitudinal dynamic loss rate is specific to the material chosen to form the core, and the loss of a material having a particularly desired longitudinal dynamic loss rate is a matter of experiment and error. Nitrile rubber and synthetic butadiene-based rubbers as well as natural rubber have longitudinal dynamic loss rates of particular interest when used in the practice of this invention. The desired structural and acoustical properties in the material of the core 16 typically exist in opposition, and the structural properties in the shaping of the window 10 of the present invention are determined by the thickness of the septum, tensile and compressive modulus, and Adjusted by core thickness and shear modulus.

The windows 10 in Figure 2 above were each made of 174 inches (174 inches) of fiberglass prepregged with 121°C curable epoxy.
It was manufactured by forming the partition walls 12 and 14 with a thickness of 0,630α). Core from natural rubber 2-17
It was formed with a thickness of 2 inches (6.35 cm). The coating layers 18 and 20 are made of B, F, Goodrich N0FQ.
IJ! , 1-1/4 inch (3.18 cm) thick from rubber. When conducting sound transmission clarity tests and sound transmission loss tests, the structure formed in this Example 1 yielded a curve shown as curve 50 in FIG.

For comparison, 1-1/4 inch thick GRPC
The performance of the 3,175 C11) was plotted as curve 52 and the performance of the 172 inch (1,27 cm) was plotted as curve 54. In FIG. 5, the horizontal axis plots frequency (Hz) and the vertical axis plots loss (decibels). Performance is determined at 21.6°C for a 5 ft x 5 ft (1.52 m) panel.

The structure made in Example 1 was then replicated, and the partition walls were made of epoxy glass [1,2
7cm) thick] and N0FOUL (1/2 inch (
1.27 cm thick). The performance of this second structure when subjected to loss testing is characterized by curve 56. For comparison, the performance of 2.1 inch thick G RP (5,334CI) is shown by curve 58 and 578 inch (1,59CII)
The performance of the steel is shown by curve 60. Test conditions and panel size were unchanged.

The windows of the present invention can be "tuned" by selection of the thickness and materials of the septum 12, 14 and core 16 to adjust a wide range of sound frequencies. Requires testing and error power.At least approx.
00) Sound waveforms with frequencies from 12 to about 50 KHz can be accompanied by amazing clarity and lack of attenuation and deformation;
and provides the window 10 with the desired structural strength.

As shown herein, the laminate structure of the present invention having a core material with a lower static and dynamic modulus than conventional window construction materials is characterized by the passage of the window through the fluid in which the window is used. or allowing dynamic decoupling of the laminate layers 12, 14, 16 in the presence of vibrations often caused by transmitted structural vibrations due to vessels carrying windows. This decoupling tends to substantially reduce the emitted noise corresponding to this "use" phase of the window. Furthermore, in the absence of service vibrations, the window remains "rigid", ie, dynamically decoupled, and thereby remains structurally "rigid".

This decoupling is particularly effective in the frequency range from about IKZ to about 20 KHz.

While the preferred embodiments of the invention have been particularly shown and described, various modifications may be made within the scope of the claims.

[Brief explanation of the drawing]

1 is a cross-sectional view of a portion of an acoustic window manufactured according to the present invention; FIG. 2 is a cross-sectional view of a portion of an acoustic window manufactured according to the present invention; FIG. 4 is a graph of the sound transmission performance characteristics of a sound waveform structure as a function of the frequency of the waveform transmitted through; FIG. 4 is a graph of the transmission loss or attenuation of a sound waveform signal as a function of frequency; Figure 5 is a graph of the sound path performance of various dome shapes as transmission loss plotted as a function of frequency. Explanation of reference numbers in the figures: 12, 14... bulkhead, 1
6...Core. FIG, 3 FIG, 4 trouble > (to the east +z+ → FIG, 5

Claims (1)

[Claims] 1. A window for the passage of a desired sound waveform comprising: i) reinforced and unreinforced thermosetting plastics and thermoplastics; ii) low density, high modulus a pair of partition walls formed from a material selected from the group consisting of metals, metal alloys, and iii) carbon composite materials; a core laminated between the partition walls, wherein the core comprises:
static shear modulus of about 200 to about 15,000 psi, about 6
Young's modulus of 00 to about 50,000 psi, elongation at break of at least about 3% and about 1,200 to about 2,000 m
a window formed from a material having a longitudinal velocity growth characteristic for a waveform of /sec; comprising said septum and core that together define a thickness of 1/2λ±25% for the desired waveform. 2. The sound waveform is at least about 0.001 m to about 1.5 m.
2. A window according to claim 1, having a λ of m. 3. The window of claim 1, wherein said core material is selected from the group consisting of natural and synthetic rubbers, elastomers, and reciprocable filled and unfilled synthetic polymers. 4. The core material has a molecular weight of about 3,000 to about 15,000
static shear modulus in psi, about 10,000 to about 50,00
4. The window of claim 3 having a Young's modulus of 0 psi and an elongation at break of at least about 6%. 5. The window of claim 4, wherein said window has a dome structural shape. 6. A window for the passage of a desired sound waveform having a λ of at least about 0.001 to about 1.5 m in an aqueous environment, the window comprising: a sandwich composed of a core laminated between a pair of septa; wherein the septum is made of i) reinforced and unreinforced thermosetting plastics and thermoplastics; ii) steel, aluminum, titanium, stainless steel, copper, nickel, beryllium, magnesium and alloys thereof; and iii) a carbon composite material; the core is formed from a material selected from the group consisting of:
00 psi static shear modulus, about 600 to about 50,000
psi, a Young's modulus of at least about 5%, an elongation at break of at least about 5%, and a longitudinal growth characteristic for a desired acoustic waveform of about 1,200 to about 2,000 m/sec; Approximately 1/2λ±2 for the sound waveform
5% thickness; characterized in that the core material is selected from the group consisting of natural and synthetic rubbers, elastomers and castable filled and unfilled synthetic polymers. 7. The core material has a molecular weight of about 3,000 to about 15,000
static shear modulus in psi, about 10,000 to about 50,00
7. The window of claim 6 having a Young's modulus of 0 psi and an elongation at break of at least about 6%. 8. The core may be made of natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chlorinated rubber,
8. The window of claim 7 formed from a material selected from the group consisting of castable polyurethanes and castable reactive liquid polymers. 9. The window of claim 8, wherein the core material is filled with a filler selected from the group consisting of minerals, polyesters, polyolefins, polyaramids, glass, polyvinyl and polyamide fibers, and carbon particulates and microspheres. 10. The window of claim 6, wherein said window has a dome structural shape. 11. The window of claim 8, wherein said window has a dome shape. 12. At least one surface of the bulkhead opposite the bulkhead surface laminated to the core has an effective thickness of a material selected from the group consisting of natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and chlorinated rubber. 7. The window of claim 6, wherein the rubber coating and comprising the thickness of the coating includes a biologically active agent in an amount sufficient to inhibit biological contamination of the window. 13. At least one surface of the partition wall opposite the partition surface laminated to the core has an effective thickness of a material selected from the group consisting of natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and chlorinated rubber. 7. The window of claim 6, wherein the rubber coating and comprising the thickness of the coating includes a biologically active agent in an amount sufficient to inhibit biological contamination of the window. 14. During impregnation of the window into the liquid, at least about 0.00
A method of manufacturing a window for the passage of a desired acoustic waveform having a desired λ of 1 to about 1.5 m, comprising: providing a sandwich consisting of a core laminated between a pair of septa;
wherein the septum is selected from the group consisting of i) reinforced and unreinforced thermosetting plastics and thermoplastics; ii) steel, aluminum, titanium, stainless steel, copper, nickel, beryllium, magnesium and alloys thereof; formed from a material selected from the group consisting of a selected low density, high modulus metal; and iii) a carbon composite material;
The core has a static shear modulus of about 200 to about 15,000 psi, a Young's modulus of about 600 to about 50,000 psi, an elongation at break of at least about 5%, and an elongation at break of about 1,200 to about 2
,000 m/sec; the sandwich defines a thickness of about 1/2λ±25% for the desired sonic shape; the core material are selected from the group consisting of natural and synthetic rubbers, elastomers and castable filled and unfilled synthetic polymers; and forming said septum and core laminate into a desired physical shape. 15. The core material is selected to have a static shear modulus of about 3,000 to about 15,000 psi, a Young's modulus of about 10,000 to about 50,000 psi, and an elongation at break of at least about 6%. 15. The method according to claim 14. 16. The method of claim 15, wherein the core material is selected from the group consisting of natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chlorinated rubber, castable polyurethane, and cast-reactive liquid polymer. 17. The method of claim 14, wherein the laminate is shaped to have a thickness of 1/2λ±15%. 18. The method of claim 14, comprising the steps of: 18. forming the septum and core laminate into a sonar dome. 19. A dome according to any preceding claim, wherein the dome is shaped to mechanically decouple in the presence of waves having a frequency of about 1 KHz to 20 KHz.