Noise-canceling headphones

Abstract

This utility model relates to personal protective equipment for workers engaged in underground mining operations, specifically to personal hearing protection against noise in underground coal mining environments. The technical result is an increased degree of hearing protection during underground mining operations. This enhanced hearing protection, particularly for miners, is achieved by absorbing mid- and high-frequency sounds through a two-layer sound-absorbing structure. The earmuffs, when used, are capable of reducing industrial noise to the specified maximum permissible noise level.

Description

[0001] The utility model relates to personal protective equipment, namely to personal hearing protection equipment against noise in underground coal mining conditions.

[0002] Noise-canceling headphones (RU patent no. 160395, published March 20, 2016) are known to contain a rigid hollow housing, a shock-absorbing cushion, and U-shaped wire brackets with hinges for securing the earcups. The shock-absorbing cushion is located on the end surfaces of the housing.

[0003] The disadvantages of this device are the limited sound insulation of the headphones, due to the mechanical properties of the housing and sound absorber; during prolonged work, the worker may experience localized disturbances in blood flow and lymph flow due to the strong pressure of the shock-absorbing rollers and the weight of the protective headphones.

[0004] Noise-canceling headphones (RU patent no. 194893, published December 26, 2019) comprise a headband, a housing with a magnetic protector, and a sound-absorbing lining. The protector is made of a flexible, elastic, sealed polymer material in the form of two parallel sheets, hermetically sealed at the edges. A constant vacuum is created between these sheets, and permanent magnets are attached to the inner sides of each sheet, with the same poles facing the sheets. The arrangement of the permanent magnets on the parallel sheets is identical and symmetrical.

[0005] The disadvantages of these earmuffs include their ineffective noise-canceling properties, as they rely solely on sound-absorbing lining to protect against hearing loss, as well as their complex and heavy design. The complex design is characterized by the presence of a closed vacuum system in the earcups, which also indirectly impacts the earmuffs' durability.

[0006] Noise-canceling headphones (RU Patent No. 160395 U1, published March 20, 2016) comprise a headband and two earcups. Each earcup is connected to the headband by two connecting nodes using U-shaped clamps. Each earcup-to-headband connection node contains a cylinder. A portion of a U-shaped clamp is inserted longitudinally into one end of the cylinder, while a C-shaped clamp is located at the other end. A sleeve with a cap and a longitudinal projection positioned between the ends of the C-shaped clamp is located within the clamp, allowing limited rotation. The sleeve contains an opening within which the earcup projection is located, allowing rotation.

[0007] The disadvantages of this device are the complexity of the design, containing a large number of elements and mechanisms, which also leads to rapid contamination and failure of the device in dusty production conditions.

[0008] Noise-canceling headphones (RU patent no. 164549, published September 10, 2016) are known that reduce the size of the headphones without losing the ability to remove the ear cushion from the earcup. The headphones comprise a headband and two earcups, each of which is connected to the headband by two connecting nodes using U-shaped clamps and locking tabs. An ear cushion is secured to each earcup. Each locking tab is located on the edge of the earcup. Each ear cushion is removable and is made of a flexible, non-elastic material that encircles the edges of the earcup. Along the entire circumference of the earcup, the distance between opposite ends of the ear cushion is less than the distance between corresponding ends of the earcup, except where the locking tabs are located, where the distance between the edges of the ear cushion is equal to the distance between corresponding edges of the earcup.

[0009] The disadvantages of this device are the limited sound insulation of the headphones, due to the mechanical properties of the housing and sound absorber; during prolonged use, the worker may experience localized disturbances in blood flow and lymph flow due to the strong pressure of the shock-absorbing rollers.

[0010] Noise-canceling headphones (RU patent no. 226029, published on 17.05.2024), taken as a prototype, are made of a non-flammable composite material, to which a protective casing made of artificial leather is attached. A rod for adjusting the length of the headphones is fixed at the bottom of the headband, on the upper surface of which there are teeth made of a composite material for fixing the fit adjustment on the ear organ. The headband is connected with the possibility of removal and rotation by a fastening to the fastening arc. The earcups are made of ABS plastic, on the upper and lower side parts of which there are longitudinal anti-slip notches. A sound absorber is fixed inside the earcups, the first layer of which is made of SPG 2540 10 acoustic polyurethane foam with a thickness of 18 to 20 mm, the second layer is made of Zvukoizol VEM 2 acoustic membrane with a thickness of 2 to 4 mm.Rectangular sound absorbers are connected by an adhesive polymer layer applied to the top surface of the second layer. Behind the sound absorbers, a free volume is created, consisting of a cylindrical pressure cushion made of SPG 2540 acoustic polyurethane foam, which is attached to the entire inner side of the earcups.

[0011] The disadvantages of this device are the insufficient resistance of sound-absorbing materials to moisture, which, if exposed for a long time, can lead to damage to the device and a decrease in the effectiveness of protection.

[0012] The technical result is to increase the degree of hearing protection and noise absorption.

[0013] The technical result is achieved in that the headband contains a steel spring, the first layer of the sound absorber is made of silicone 15 mm thick, and the second is made of foamed polypropylene with a thickness of 4 to 6 mm, on the outside of each earcup there are holes in which two-layer acoustic valves are installed, the first layer of which is made of silicone 2 mm thick, and the second is made of foamed polypropylene 4 mm thick.

[0014] The noise-canceling headphones are explained by the following figures:

[0015] Fig. 1 - general view of the device;

[0016] Fig. 2 - side view;

[0017] Fig. 3 - acoustic shell, where:

[0018] 1 - headband,

[0019] 2 - earphone cup,

[0020] 3 - pressure roller,

[0021] 4 - acoustic valve,

[0022] 5 - first layer of the valve,

[0023] 6 - the second layer of the valve,

[0024] 7 - fastening,

[0025] 8 - the first layer of sound absorber,

[0026] 9 - the second layer of sound absorber,

[0027] 10 - free volume of the earcup,

[0028] 11 - protective net,

[0029] 12 - protective cover,

[0030] 13 - adjustment rod,

[0031] 14 - teeth.

[0032] The earmuffs for underground mining operations consist of a headband 1 made of a steel spring, onto which a protective cover 12 made of imitation leather is fixed. A rod 13 for adjusting the length of the headphones is fixed at the bottom of the headband 1. On the upper surface of the rod 13 for adjusting the length of the headphones, made of a composite material, teeth 14 are made with the ability to fix the fit adjustment on the ear organ. The headband 1 is connected so as to be removable and rotated by a fastener 7. The earcups 2 are connected so as to be removable and rotated by a fastener 7. The earcups 2 are made of polyvinyl chloride and are a hollow structure in which a two-layer sound-absorbing structure is fixed. The first layer of the sound-absorbing material 8 is made of dense silicone 15 mm thick. The second layer of the sound-absorbing material 9 is made of foamed polypropylene with a thickness of 4 to 6 mm.The sound absorbers are made in the form of a rectangle, which are connected to each other by an adhesive polymer layer, which is applied to the upper surface of the second layer. A free volume 10 is formed behind the sound absorbers. On the outer side of each earcup 2, openings are made, into which acoustic valves 4 are installed. The acoustic valve 4 is made in two layers, the first layer 5 of the acoustic valve 4 is made of dense silicone 2 mm thick. The second layer 6 of the acoustic valve 4 is made of foamed polypropylene 4 mm thick. The pressure shock-absorbing roller 3 is made in the form of a cylinder and is fixed on the entire inner side part of the earcups 2. The pressure shock-absorbing roller 3 is made of acoustic polyurethane foam SPG 2540. On the inner side of the earcup 2, over the first layer of the sound absorber, a protective mesh of the sound absorber 11 on a fabric base is fixed.

[0033] The device operates as follows. The length of the headphones is adjusted using the length adjustment rod 13 and teeth 14. The fastening 7 is a pin connection to ensure mobility and ensure a comfortable fit of the protective headphones. Hearing protection from low frequencies in the range from 125 Hz to 500 Hz is ensured by the pressure of the shock-absorbing roller 3, made of acoustic polyurethane foam SPG 2540 and the first layer of sound absorber 8 - dense silicone 15 mm thick. A reduction in the likelihood of occupational sensorineural hearing loss is ensured by reducing the impact of medium and high frequencies by the second layer of sound absorber 9 made of foamed polypropylene 4 to 6 mm thick, which is part of the earcup 2.At frequencies above 4000 Hz, additional noise reduction in the headphones is achieved by interference summation of sound waves in free volume 10 due to the phase shift of the sound wave oscillations in the open-pore cellular structure. To protect the first layer of sound absorber 8 from contamination and physical impact, a protective mesh 11 is installed on top.

[0034] The thickness of the foamed polypropylene materials was determined based on numerical calculations using the licensed COMSOL Multiphisics Acoustics software package and is presented in Table 1.

[0035] Table 1 - acoustic measurement results of 15mm thick dense silicone and 6mm thick foamed polypropylene.

[0036] Frequency, Hz 125 250 500 1000 2000 4000 8000 Material Sound absorption coefficient, α Two-layer structure 0,38 0,41 0,67 0,79 0,85 0,84 0,81

[0037] The structure consisting of the first sound absorber layer 8 and the second sound absorber layer 9 is characterized by the acoustic efficiency shown in Table 2 and Table 3.

[0038] Table 2 - Noise level reduction in octave bands with geometric mean frequencies with the valve open.

[0039] Octave band, Hz 125 250 500 1000 2000 4000 8000 Attenuation, dB 12 14 10 5 10 15 20

[0040] Table 3 - Noise level reduction in octave bands with geometric mean frequencies with the valve closed.

[0041] Octave band, Hz 125 250 500 1000 2000 4000 8000 Attenuation, dB 13 16 21 27 33 39 43

[0042] With the acoustic valve closed, noise levels are reduced from 13 dB to 43 dB in the frequency range from 250 to 8000 Hz. The dual-layer structure provides high noise absorption at low, medium, and high frequencies, effectively protecting hearing from the industrial noise of mining equipment in underground mining environments. With the acoustic valve open, sound level reduction is minimal at 1000 Hz, which is necessary for speech recognition during production operations.

[0043] Hearing protection, particularly for miners, is enhanced by the absorption of mid- and high-frequency sounds by the dual-layer structure of the sound absorber. Using these earmuffs can reduce industrial noise to the specified maximum noise level.

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