65results about How to "Improved sound absorption" patented technology

The invention discloses a sound-absorbing coating material, wherein every 100 parts by mass of coating contains 5-50 parts by mass of sound-absorbing function materials, 0.1-35 parts by mass of flame retardant materials, 10-40 parts by mass of binding materials, and the balance of an inorganic filling, an assistant and water in a common coating. The sound-absorbing function materials are selected from one or composite of some of materials such as slag fibers, mineral fibers, glass fibers and wood fibers, with fiber structures, and the sound-absorbing function materials are subjected to waterproof modification treatment. According to the invention, NRC (Noise Reduction Coefficient) of the coating material is tested to be more than 0.4 by using a standing wave tube method, and the sound-absorbing coating material has a good sound-absorbing denoising performance, excellent flame resistance and low heat conductivity coefficient, can be used for reducing the energy consumption of a building, is an environmental-friendly functional sound-absorbing coating material integrated with functions of sound absorption, flame resistance and decoration, and can be used on the surface of the building.

The invention provides a noise reduction sound absorption layer. The sound absorption layer comprises a keel and a sound absorption component, wherein the component comprises a micro-perforated panel 2, non-woven fabrics 3, a bi-component fiber mat 1 and a back plate 4, which are sequentially arranged along the direction from a noise source to a wall. The sound absorption principle of the noise reduction sound absorption layer couples the effects of bi-component resistive sound absorption and dual-layer resonance sound absorption; low-frequency noise of a substation transformer and a high-voltage reactor is effectively absorbed, and thus the target of reducing sensitive points on the boundary of a transformer substation and sensitive points out of the transformer substation is achieved.

The invention provides a compound damping foam rubber material. The material is prepared from rubber, reinforcing filling and addition agents, wherein the addition agents comprise a vulcanizing agent, a dispersant, an anti-scorching agent, an anti-ageing agent, an accelerant, a secondary accelerant and a softening agent; the rubber is selected from at least two of silicone rubber, nitrile butadiene rubber, butadiene rubber, isoprene rubber and ethylene propylene rubber; and the addition agents also comprise a foaming agent. The compound damping foam rubber material provided by the invention has the advantages of light weight, cost reduction, good transformer oil resisting performance, good electric insulating performance and the like; a pore structure generated by foaming and the rubber material have a viscoelastic damping synergistic effect to enhance sound energy dissipation and improve noise-reduction performance of the compound damping foam rubber material; and the compound damping foam rubber material can be used as a sound-absorption and noise-reduction material to be applied to vibration absorption and noise reduction of a transformer body, and has remarkable economic and social benefits.

The invention relates to a sound absorption composite structural material and a preparation method thereof. The material comprises the components of a chlorinated polyethylene / seven-hole hollow polyester staple fiber composite material and a perforation plate, wherein the mass ratio of chlorinated polyethylene to a seven-hole hollow polyester staple fiber is 4 to 1. The preparation method comprises the following steps of: (1) perforating stainless steel according to a triangular distribution mode, cleaning the surface of the stainless steel, and thus obtaining the perforation plate; and (2) flatly coating an adhesive on the surface of the chlorinated polyethylene / seven-hole hollow polyester staple fiber composite material, and thus obtaining the material. The sound absorption composite structural material can effectively absorb sound energy, and two different sound absorption mechanisms of a porous material and film resonance vibration can be fully used for expanding a sound absorption effect field in a cooperation way along with the increase of the number of structural layers; and the material is easy to prepare, and the material and the preparation method are suitable for industrial production.

The invention provides a low-frequency broadband sound absorption material based on an asymmetric film-type sub-wavelength structure. The material comprises several sound absorption units. Each sound absorption unit comprises a framework, a flexible film and eight mass blocks with different weights. The framework is arranged in a window style. The flexible film is fixed to the framework in a tensioning mode so as to form four equivalent noise elimination units. Each two blocks of the eight mass blocks form one group and the groups of the blocks are fixed to films of the noise elimination units in a one-to-one correspondence mode respectively. The several sound absorption units are expanded towards peripheries in a framework plane and are spliced to form the low-frequency broadband sound absorption material based on the asymmetric film-type sub-wavelength structure. A whole structure is a quadrilateral sound absorption unit material mainly formed by the flexible film and a mass block system. Because of asymmetric distribution of the mass blocks, a dynamic characteristic shows that a plurality of frequency points with zero equivalent mass density are possessed, which means that a plurality of peak values of sound absorption coefficients are possessed. Under an influence of an asymmetric mode, total elastic strain energy of the structure is higher than strain energy of a symmetric mode in a full frequency range.

The invention belongs to the technical field of noise reduction, and discloses a sound absorbing device. The sound absorbing device comprises a sound absorbing unit body, and the sound absorbing unitbody comprises a porous sound absorbing device and a resonant sound absorbing device; the porous sound absorbing device comprises a porous sound absorbing layer, and a tube cavity is formed in the porous sound absorbing layer; the resonant sound absorbing device comprises a resonant tube and a sound absorbing tube; the resonant tube is mounted in the tube cavity in a matched mode; and a through hole is formed in the top of the resonant tube, the sound absorbing tube is mounted in the through hole in a matched mode, and both the two ends, in the resonant tube, of the sound absorbing tube are open. The sound absorbing device is provided with the porous sound absorbing device and the resonant sound absorbing device, thus a parallel sound absorbing structure is formed, and the overall sound absorbing performance to low, medium and high frequency wide band sound waves is good; and the sound absorbing performance can be improved within the limited thickness.

The application discloses a sound-proof shield of a motor and an apparatus with a motor. The apparatus comprises a motor and a motor sound-proof shield. A composite sound-absorption layer is arranged inside the motor sound-proof shield and consists of a damping sound-absorbing layer, a perforated plate, sound-absorbing cotton and a sound insulation board. The space encircled by the sound insulation board and the perforated plate is filled with the sound-absorbing cotton; and the damping sound-absorbing layer is in contact with the outer side surface of the perforated plate. Because the composite sound-absorption layer is arranged inside the motor sound-proof shield, the motor sound-proof shield covers the outer side of the motor, and thus the motor is enclosed in the space formed by the motor sound-proof shield, the degree of outward radiation of noises of the motor can be reduced; with the composite sound-absorption layer, the sound absorption performance of the motor sound-proof shield can be improved and the volume of noises can be reduced, so that the noise value of equipment having the motor can be reduced.

The invention discloses a preparation method of porous ceramsite, a product and an application of the porous ceramsite in a concrete subway track acoustic board, and the preparation method comprises the following steps: uniformly mixing fly ash, cement, lime and gypsum, and carrying out ball milling treatment to obtain initial powder after ball milling; ball-milling an original expanded perlite raw material to obtain ball-milled expanded perlite powder; uniformly mixing the ball-milled initial powder with the ball-milled expanded perlite powder according to a mass ratio of 100:(4-8) to obtaina mixed raw material; granulating the mixed raw materials; and putting the pelletized ceramsite into an autoclave sterilizer, and carrying out autoclave treatment to obtain the porous ceramsite. According to the invention, a raw material pretreatment mechanism and an autoclaved sterilization maintenance mode are added, and proper expanded perlite is added to well control the concentration of a low-temperature decomposition foaming agent solution; through the synergistic effect of the preparation processes, the apparent porosity of the prepared porous ceramsite is 58.01%, the cylinder compressive strength is 2.70 Mpa, and the porous ceramsite can be applied to concrete subway rail acoustic panels.

The invention relates to an acoustic panel with a unit structure. The acoustic panel comprises an ultramicropore acoustic panel, a side edge plate and an acoustic back plate. The edge part of the ultramicropore acoustic panel is connected with the acoustic back plate through the side edge plate to form a sound absorption resonant cavity. The acoustic panel is characterized in that an sound absorption metal film parallel to the sound absorption resonant cavity or an sound absorption metal film with nano microspheres is arranged in the sound absorption resonant cavity. The acoustic panel not only has the advantages of wide sound absorption bandwidth and good noise reduction effects, but also has the advantages of simple structure and simplicity, convenience and reliability in process manufacture and assembly use. The acoustic panel is suitable for the occasions in various buildings where ceiling hanging and wall decoration are required, and particularly suitable for the occasions where high sound absorption is required.

The invention relates to the preparation method of an acupuncturing 3D sound-absorbing body. The preparation method comprises the following steps:(a) weighting the first polyester staple fiber and fiber A respectively; (b) then entering into the cotton rolling equipment to carry out opening and mixing;(c) the fiber after processed by the cotton rolling equipment entering into a cotton mixing machine for further uniform mixing;(d) entering into the combing equipment and forming a fiber network after opening; (e) the fiber network entering into a stacking device for stacking;(f) forming cellucotton after first acupuncturing of the stacked fiber network; (g) placing a cotton blanket on the cellucotton, then carrying out the second acupuncturing to form into a acupuncturing cotton blanket;(h) cutting the acupuncturing cotton blanket into acupuncturing cotton blanket blocks by the cutting equipment; (i) enabling the acupuncturing cotton blanket blocks to enter into the heat setting equipment for heat setting; and(j) squeezing the acupuncturing cotton blanket blocks by a mould, so as to obtain the acupuncturing 3D sound-absorbing body. The 3D sound-absorbing body provided by the invention has the effects of sound absorption, noise reduction and decoration.

The invention discloses a micro-nano combined active-passive mixed sound absorption structure and a control method thereof. The micro-nano combine active-passive mixed sound absorption structure is characterized in that nano tubes are uniformly filled in a sound absorption porous material to form a passive sound absorption structure, the front plane of the passive sound absorption structure is exposed in a vertically incident sound wave, and the back of the passive sound absorption structure is an elliptic plane; and the elliptic plane of the passive sound absorption structure is adhered with a piezoelectric film with the thickness in micron grade to form an active control execution device of the mixed sound absorption structure. In the invention, active noise control and the improved sound absorption material are combined to a specific mixed sound absorption structure, thus the effective sound absorption frequency band is greatly expanded, the volume of the sound absorption structure is greatly reduced, the active control voltage is reduced, and the control effect is better.

The invention discloses a parameter design method of a tire cavity resonance noise attenuation device. According to the parameter design method, porous materials used by the tire cavity resonance noise attenuation device are equivalent to fluid meeting a Delany-Bazley theoretical model, a characteristic equation of sound pressure in a tire cavity is calculate according to boundary conditions existing in the tire cavity, cavity resonance frequency and a characteristic value corresponding to the cavity resonance frequency are acquired according to the characteristic equation of the sound pressure, and the thickness and the flow resistance rate of the porous materials are designed. According to the method, parameter selection and design of the noise attenuation device is more optimized when tire cavity resonance noise is effectively reduced, and bases are provided for material parameter design of the tire cavity resonance noise attenuation device.

The invention discloses a composite sound absorption structure for improving set low frequency sound absorption performance, and belongs to the technical field of acoustics, the structure is formed by an upper felt layer, a middle felt layer and a lower felt layer which are fixedly connected in sequence; the upper felt layer, the middle felt layer and the lower felt layer are metal fiber felts; wherein the upper felt layer and the lower felt layer has the same thickness which is 1.5mm-5mm; the thickness of the middle felt layer is equal to or lower than the same of the upper felt layer and the lower felt layer; more than one through holes are uniformly arranged on the surface of the middle felt layer, the axis direction of the through holes is the same with the height direction of the middle felt layer; thin films are fixed to the internal through holes; the shape of each thin film is the same with the radial section shape of each through hole, and the thin films in all through holes are in the same plane; a mass block is fixed to each thin film; the structure is used for improving the sound absorption performance of the metal fiber felt in 0-1500Hz low frequency range, an acoustic metamaterial interlayer and the mass block are introduced to improve the material set low frequency sound absorption performance, and the structure has characteristics of adjustable frequency and good sound absorption performance.

The invention discloses a half-perforated foam sound absorbing structure with variable connectivity rate, wherein the connectivity rate is gradually increased along the acoustic wave incidence direction, and the variance is that the connectivity rate is abruptly increased along the acoustic wave incidence direction or linearly increased along the acoustic wave incidence direction; and when the acoustic wave is propagated from a communicating pore to a main pore, as the volume is abruptly expanded for 10 times to even dozens of times, the acoustic wave kinetic energy is attenuated due to the abrupt variance of the volume, the acoustic energy quickly works externally so as to be converted into heat energy for dissipation. Compared with the conventional isotropic structure, the connectivity rate variance structure has lower connectivity rate at the front end, so that the sound absorbing effect is increased; the higher connectivity rate at the rear end enables the resonant frequency of the structure to shift to low frequency, so as to improve the integral sound absorbing property of the half-perforated foam sound absorbing structure with variable connectivity rate. Compared with the isotropic half-perforated foam sound absorbing structure, the structure has the advantages that the low and medium frequency sound absorbing property is improved for 30% to 50%.

The invention discloses an index gradient acoustic covering layer with embedded scatterers and cavities. The index gradient acoustic covering layer comprises a matching layer (1), a sound absorption layer (2) and a steel backing (3). The matching layer is made of glass fiber reinforced plastics, the sound absorption layer is formed by arranging a plurality of rectangular units in an array mode, each unit takes silicone rubber with the density of 1000 kg / m<3> as a base body, two layers of steel cylinder scattering bodies and two layers of cylinder cavities are embedded in the base body, and the embedded steel cylinder scattering bodies and the cylinder cavities are vertically arranged along the center line positions of the units. Each layer of scatterers or cavities has different equivalent densities, the whole scatterers or cavities are in index gradient distribution, and two sides of sound absorption are sealed. The steel backing is used for simulating an underwater vehicle shell. Sound absorption layer units are bonded together through cold pressing by coating an adhesive among the sound absorption layer units, and the matching layer, the sound absorption layer and the steel backing are combined into a whole through cold pressing by coating an adhesive among the matching layer, the sound absorption layer and the steel backing as well. According to the gradient design, the low-frequency sound absorption bandwidth can be effectively widened, and the problem that the low-frequency sound absorption frequency band of an acoustic covering layer is narrow is solved.

The invention introduces a polyurethane anechoic tile product and a preparation method thereof. A thick plate of a polyurethane anechoic tile is prepared into a slabbed construction which is 40-60mm thick with a vocal tract hole structure and the size can be determined according to the size of a die. The tile can be prepared by simulating 10 times of the area of the existing acoustic tile, so that the single tile area of the anechoic tile is effectively improved, the joint of the anechoic tile is effectively reduced and the damage probability of the anechoic tile is effectively reduced. The polyurethane anechoic tile prepared by the preparation method realizes the material performance and the water acoustic absorption performance of the existing rubber anechoic tile and is technically probable of replacing original rubber anechoic tile. The tile is the invention which is suitable for the technical field of coating anechoic tiles outside ships and has an actual application value.

The invention provides an automobile front wall noise elimination part and a preparation method thereof. The noise elimination part sequentially comprises a sound insulation layer, a bonding layer anda noise elimination layer from outside to inside; the sound insulation layer and the noise elimination layer are composed of composite fibers; the composite fibers comprise first fibers and second fibers; the fineness of the first fibers is larger than that of the second fibers; the length of the second fibers is 30-50 mm; the linear density of the second fibers is 0.05-0.5 dtex. According to theautomobile front wall noise elimination part, the sound insulation layer and the noise elimination layer are arranged, so that the automobile front wall noise elimination part has excellent sound absorption performance and sound insulation performance at the same time, particularly, the superfine fibers are adopted, the noise elimination layer can form a loose porous structure, the sound absorption performance is greatly improved, sound energy can be consumed through vibration of the superfine fibers, and the sound absorption performance and the sound insulation performance are improved; by using the superfine fibers, the weight of the part can be reduced, and the light weight of an automobile is realized.

The invention provides a multi-stage foam sound absorption black body material for the first time, graphene aerogel is introduced into a commercialized polymer foam skeleton by using a solvent plasticizing foaming technology, so that ultrathin graphene drums are embedded into the foam skeleton, and when sound waves enter the foam black body, a large number of graphene drums generate a violent resonance effect, so that attenuation of the sound waves is rapidly achieved, and in combination with friction loss of a porous structure of the polymer foam to the sound waves, the sound absorption black body foam material has excellent sound absorption performance in a broadband range. The scheme is based on a commercial foam material, the method is simple, the cost is low, and the potential of wide industrial application is achieved.

The invention relates to the field of sound absorption and insulation materials, in particular to a sand-coated sound absorption board based on a gypsum board. The sand-coated sound-absorbing board based on the gypsum board comprises a sound absorption coating, a gridding cloth and a gypsum board base plate, wherein the sound absorption coating, the gridding cloth and the gypsum board base plate are arranged in sequence. The compositions of the sound absorption coating comprise filler and inorganic binder, and the filler comprises silica sand and resin particles. The sand-coated sound-absorbing board based on the gypsum board has excellent sound absorption ability.

The invention discloses a resonator for lithography equipment noise reduction. The resonator includes: an inner cavity and a pipe orifice connected to the inner cavity. The pipe orifice consists of an outer wall, an air layer, a sound absorption layer and an inner wall perforated plate from the outside in sequentially. The resonator provided by the invention can realize adjustable resonant frequency, and makes the resonant frequency similar to that of a noise source, thus reaching the technical effect of effective sound absorption.

The invention relates to a frame plate buckling type railway metal sound barrier, and the model is a TKZP railway metal sound barrier. The frame plate buckling type railway metal sound barrier is suitable for the fields of high-speed railways, intercity railways, passenger transport lines, rail transit and the like, and belongs to the technical field of vibration and noise treatment in environmental protection. The frame plate buckling type railway metal sound barrier mainly comprises a metal sound barrier unit board panel, a back board, a profile framework, a sound absorption component and arubber part, wherein the profile framework is connected with the panel / the back plate to form a unit plate main body structure by adopting a rivet-free buckling mode. The frame plate buckling type railway metal sound barrier comprises a top unit plate, a standard unit board and a bottom unit board, wherein the top unit board, the standard unit board and the bottom unit board are sequentially arranged on the sound barrier steel stand column from top to bottom. According to the frame plate buckling type railway metal sound barrier, the load of the train pulsation load to the sound barrier and asteel stand column can be effectively weakened, and the load-reducing effect is obvious; and the overall rigidity of a sound absorption material is improved, pressure fiber cement board support is not needed, the weight of the sound barrier plate is reduced, the safety of the sound barrier structure is improved, and the anti-fatigue life is prolonged.

The invention discloses a bionic non-smooth surface polyurethane foam board with cylindrical pits. The bionic non-smooth surface polyurethane foam board comprises a base board, the cylindrical pits are arranged on the upper surface of the base board, the cylindrical pits and the base board are structurally integrated and made of polyurethane, and the cylindrical pits include uniformly arranged semi-cylindrical pits and semi-elliptic cylindrical pits. The polyurethane foam board can show excellent sound absorption performances within a narrow thickness range, so that the purposes of sound absorption and noise reduction are achieved.

The invention provides a bulkhead sound insulation and thermal insulation composite structure. The bulkhead sound insulation and thermal insulation composite structure comprises a first panel, a firstcellular board, a first perforated board, a thermal insulation material layer, a second perforated board, a second cellular board and a second panel, wherein the first panel, the first cellular board, the first perforated board, the thermal insulation material layer, the second perforated board, the second cellular board and the second panel are sequentially connected in a bonding mode. A resonance sound absorption structure is formed in the composite structure, the sound absorption performance is improved obviously, compared with a traditional bulkhead structure, and the sound absorption performance of the composite structure is improved obviously due to the fact that sound absorption action enables sound waves penetrating through the composite structure to be reduced effectively. Meanwhile, the introduction of a cellular structure plays a role of obstructing heat transmission, the thermal insulation performance of the composite structure is improved, the rigidity of the composite structure is greatly improved, requirements for a supporting structure are greatly relieved, installation and application are facilitated, and the weight of a total structure is reduced. Compared with an existing sound insulation structure, the thermal insulation material layer is additionally arranged in the composite structure, and the thermal insulation performance of the integral structure is greatly improved and the sound insulation performance of the integral structure can be obviously improved at the same time.

The invention relates to a preparation method of a waste rubber-based damping vibration attenuation sound-absorbing composite material and belongs to the technical field of sound-absorbing materials.A polyurethane fiber is subjected to pre-oxidation, activation and carbonization treatment to obtain polyurethane-based porous carbonized fiber, so that the sound absorption performance of the composite material is obviously improved due to the addition of the polyurethane-based porous carbonized fiber; the polyurethane-based porous carbonized fiber is introduced into a hybrid system, on one hand,air is introduced into the material by utilizing the hollowing property of the fiber, meanwhile a crystalline fiber network structure is formed through fiber crystallization induction, the problem ofpoor mechanical property of a common sound absorption material is solved, and the sound absorption property of the material is improved by means of the crystalline fiber network. The waste rubber-based damping vibration attenuation sound-absorbing composite material is prepared into the honeycomb composite material, and the honeycomb composite material has excellent performances of energy absorption, vibration reduction, energy storage and the like. By adding white carbon black, the mechanical property of the waste rubber-based damping vibration attenuation sound-absorbing composite materialis improved effectively.

The invention discloses a low-frequency micro-perforated sound-absorbing composite material and a manufacturing method thereof. The composite material comprises ethylene propylene diene monomer (EPDM) and zeolite powder, and the mass ratio of EPDM to zeolite powder is 80-100:10-30. The composite material is provided with micro-pores. The thickness of the composite material is 1 to 3 mm; the density is 9.9 to 15.9 g / cm3; the porosity is 0.5 to 2.5%; and the diameter of micro-pores is in a range of 0.5 to 1 mm. The preparation method of the composite material comprises steps of mixing, hot-press moulding, and micro-punching. The provided composite material has the advantages of better structure, better sound absorbing performance, lower production cost, and wider application range, can generate more economic benefits, and is more suitable for industrial production, popularization, and application.

The invention discloses a folded plate buckling type railway metal sound barrier unit plate, and belongs to the technical field of vibration and noise treatment in the field of environmental protection. The folded plate buckling type railway metal sound barrier unit plate is composed of a bent panel (comprising an upper side plate, a lower side plate, a left side plate and a right side plate), a bent back plate (comprising an upper side plate, a lower side plate, a left side plate and a right side plate), a supporting profile (comprising an end vertical support, a middle vertical support and atransverse support), a sound absorption assembly and a rubber part (comprising a decoupling rubber pad and an inter-plate rubber pad and a bending panel and the bending back plate are buckled in a rivet-free mode and are pressed and meshed through elastic pretightening force). The bending face plate and the bending back plate are buckled in a rivet-free mode and are pressed and meshed through elastic pre-tightening force to form a unit plate main body structure. The supporting sectional materials are clamped in the trapezoidal clamping grooves of the upper side plate and the lower side plate,the deformation resistance of the unit plates is enhanced, the meshing locking stability of the panel and the back plate is enhanced, and the supporting sectional material lateral clamping grooves and the trapezoidal clamping grooves of the upper side plate and the lower side plate achieve closed clamping and fixing of the sound absorption cotton. The folded plate buckling type railway metal sound barrier unit plate is light in weight, good in stress, firm in fixation of the sound absorption cotton, excellent in fatigue resistance, good in noise reduction effect and easy to assemble.

The invention discloses a method for preparing a sound-absorbing material through doping of core-shell microspheres and aims to solve the problem that an existing resin matrix material has poor sound absorption performance. The method comprises steps as follows: bubbles are removed from a polyurethane prepolymer; 3,3'-dichloro-4,4'-diaminodiphenylmethane is dissolved into a liquid state, and liquid-stage 3,3'-dichloro-4,4'-diaminodiphenylmethane is obtained; core-shell nanoparticles with vibratile inner cores, liquid-state 3,3'-dichloro-4,4'-diaminodiphenylmethane, toluene and the polyurethane prepolymer are mixed, a reaction system is obtained and poured into a mold, the reaction system and the mold are transferred into a vacuum drying box together after the bubbles are removed, gradient heating curing and demolding are performed, and a core-shell nanoparticle / polyurethane composite is obtained. Sound-absorbing effects at different frequencies can be obtained by preparing core-shell structures with different particle sizes.

The invention discloses a sound-absorbing coating material, wherein every 100 parts by mass of coating contains 5-50 parts by mass of sound-absorbing function materials, 0.1-35 parts by mass of flame retardant materials, 10-40 parts by mass of binding materials, and the balance of an inorganic filling, an assistant and water in a common coating. The sound-absorbing function materials are selected from one or composite of some of materials such as slag fibers, mineral fibers, glass fibers and wood fibers, with fiber structures, and the sound-absorbing function materials are subjected to waterproof modification treatment. According to the invention, NRC (Noise Reduction Coefficient) of the coating material is tested to be more than 0.4 by using a standing wave tube method, and the sound-absorbing coating material has a good sound-absorbing denoising performance, excellent flame resistance and low heat conductivity coefficient, can be used for reducing the energy consumption of a building, is an environmental-friendly functional sound-absorbing coating material integrated with functions of sound absorption, flame resistance and decoration, and can be used on the surface of the building.