Acoustic mirror

Author: d | 2025-04-25

The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a

What is Acoustic Mirror?, Acoustic signature

Design of the combiner is composed of two prisms sandwiching a thin layer of silicone oil [31]. Then, its improved version is made of a rhomboid prism and a right-angle prism, which overcomes the series of acoustic insertion loss induced by the transforming from longitudinal-mode wave to shear-mode wave at the interface [17,32]. Customized ring-shaped focused ultrasonic transducer with a central hole to pass the optical beam is also designed to achieve optical-acoustic confocal alignment [2,20]. Furthermore, optically-transparent focused ultrasound transducers could be considered as its advanced solution [33,34] to make PAM highly integrated, and it will have great potential when the processing costs is reduced. A parabolic acoustic mirror was combined with an optical lens that has a large optical numerical aperture (NA) together to realize a submicron-resolution reflection-mode OR-PAM [23]. This combiner aimed to achieve a large optical NA, and showed good acoustic potential. Additionally, another kind of combiner is arranging a thin glass plate or perforated acoustic mirror to redirect the ultrasonic beam propagating in water to a focused ultrasonic transducer, and a confocal laser beam can pass through the transparent glass plate [26,27] or the central hole [28] to achieve confocal alignment. In a word, performance of OR-PAM is closely related to the optical-acoustic combiner. A good combiner usually requires low optical disorders, low acoustic insertion loss, strong acoustic focusing, to ensure superior optical resolution, good PA excitation efficiency, and high acoustic detection sensitivity.In this study, we propose an optical-acoustic combiner composed of a flat acoustic reflector and an off-axis parabolic acoustic mirror (OPM) with a conical bore. The optical beam can be undistorted focused on the sample through the conical bore. The OPM provides strong acoustic focusing with a large acoustic NA. To realize the large acoustic NA, the structure of the parabolic mirror used in our study is different from the reported one [23]. Additionally, in order to facilitate the placement of the transducer, we have designed a sound path with two reflection in the combiner. In comparison to the other methods, the entire acoustic propagation path from the source to the transducer in our combiner is in the water, which ensures low insertion loss and a better detection sensitivity. Additionally, the proposed combiner does not rely on customized ultrasound transducer. Commonly used commercial transducers are suitable. We demonstrated the advantage and practicality of the proposed design by using numerical simulations, phantom measurement, and in vivo imaging experiments. 2. Materials and Methods 2.1. Experimental SetupThe Nd:YAG laser (EXPL-532-2Y, Spectra-Physics Inc., Santa Clara, CA, USA) worked at a wavelength of 532 nm and the repetition rate was set at 10 kHz. Haemoglobin has strong optical absorption near 532 nm, and this laser will benefit imaging

Adjustable acoustic pattern controlled by Acoustic mirrors

Photoacoustic Microscopy Using High-Speed Alternating Illumination at 532 and 1064 Nm. J. Biophotonics 2018, 11, e201700210. [Google Scholar] [CrossRef]Tian, C.; Zhang, W.; Mordovanakis, A.; Wang, X.; Paulus, Y.M. Noninvasive Chorioretinal Imaging in Living Rabbits Using Integrated Photoacoustic Microscopy and Optical Coherence Tomography. Opt. Express 2017, 25, 15947–15955. [Google Scholar] [CrossRef]Qi, W.; Jin, T.; Rong, J.; Jiang, H.; Xi, L. Inverted Multiscale Optical Resolution Photoacoustic Microscopy. J. Biophotonics 2017, 10, 1580–1585. [Google Scholar] [CrossRef] [Green Version]Chen, Q.; Xie, H.; Xi, L. Wearable Optical Resolution Photoacoustic Microscopy. J. Biophotonics 2019, 12, e201900066. [Google Scholar] [CrossRef]Zhang, X.; Ding, Q.; Qian, X.; Tao, C.; Liu, X. Reflection-Mode Optical-Resolution Photoacoustic Microscopy with High Detection Sensitivity by Using a Perforated Acoustic Mirror. Appl. Phys. Lett. 2018, 113, 183706. [Google Scholar] [CrossRef]Qiu, T.; Yang, J.; Pan, T.; Pan, T.; Peng, C.; Jiang, H.; Luo, Y. Assessment of Liver Function Reserve by Photoacoustic Tomography: A Feasibility Study. Biomed. Opt. Express 2020, 11, 3985–3995. [Google Scholar] [CrossRef]Dai, X.; Yang, H.; Jiang, H. In Vivo Photoacoustic Imaging of Vasculature with a Low-Cost Miniature Light Emitting Diode Excitation. Opt. Lett. 2017, 42, 1456. [Google Scholar] [CrossRef]Maslov, K.; Zhang, H.F.; Hu, S.; Wang, L.V. Optical-Resolution Photoacoustic Microscopy for in Vivo Imaging of Single Capillaries. Opt. Lett. 2008, 33, 929. [Google Scholar] [CrossRef]Hu, S.; Maslov, K.; Wang, L.V. Second-Generation Optical-Resolution Photoacoustic Microscopy with Improved Sensitivity and Speed. Opt. Lett. 2011, 36, 1134. [Google Scholar] [CrossRef] [Green Version]Park, S.; Kang, S.; Chang, J.H. Optically Transparent Focused Transducers for Combined Photoacoustic and Ultrasound Microscopy. J. Med. Biol. Eng. 2020, 40, 707–718. [Google Scholar] [CrossRef]Fang, C.; Hu, H.; Zou, J. A Focused Optically Transparent PVDF Transducer for Photoacoustic Microscopy. IEEE Sens. J. 2020, 20, 2313–2319. [Google Scholar] [CrossRef] Figure 1. Schematic diagram of optical-resolution photoacoustic microscopy (OR-PAM) setup. FC: fiber coupling, SMF: single mode fiber, CL: collimating-mirror, BS: beam splitter, PD: photodiode, DAQ: data acquisition. Dotted box gives the details of the optical–acoustic combiner. OL: objective lens, OPM: off-axis parabolic acoustic mirror, UT: ultrasonic transducer, FR: flat acoustic reflector. Figure 1. Schematic diagram of optical-resolution photoacoustic microscopy (OR-PAM) setup. FC: fiber coupling, SMF: single mode fiber, CL: collimating-mirror, BS: beam splitter, PD: photodiode, DAQ: data acquisition. Dotted box gives the details of the optical–acoustic combiner. OL: objective lens, OPM: off-axis parabolic acoustic mirror, UT: ultrasonic transducer, FR: flat acoustic reflector. Figure 2. Profile map of the OPM, CA: central axis, D: diameter; OAD: off-axis distance; PFL: parent focal length; RFL: reflected focal length. Figure 2. Profile map of the OPM, CA: central axis, D: diameter; OAD: off-axis distance; PFL: parent focal length; RFL: reflected focal length. Figure 3. Two kinds of acoustic focusing schemes. (a) A spherically-focused transducer combined with a flat acoustic reflector. (b) A

The Acoustic mirror by Like Mirror: The solution to isolate

Glass Doors & Open Shelves for Living Room, Bedroom & Home Theater, White ITEM SOLD AS-IS. PLEASE REVIEW ALL PHOTOS AND PREVIEW THE ITEM IF IN DOUBT ABOUT ITS CONDITION, COLOR, SIZE, OR CORRECTNESS. ITEM IS NON-REFUNDABLE. RETAIL $661.99 About this item Brand: TURRIDU Color: White Special Feature: Durable, Anti-Dumping Device, Tempered Glass Accents Style: Modern Number of Doors: 2 Shape: Rectangular Item Weight: 228.5 Pounds Item Number: WF307880AAK Subtle Luxury Aesthetic: Boasting smooth lines, pure hues, and tempered glass accents, this TV stand set imbues your living room with an air of understated luxury. Its refined design complements any decor, creating a sophisticated and inviting atmosphere. Comprehensive Storage Solutions: This wall unit boasts a spacious 66-inch console, two pier units, and an overhead bridge, offering ample storage options for all your entertainment and display needs. From TVs to books, wine, and decorations, everything has its place. Lot - 74 Costway 59''Full Length Body Mirror Aluminum Frame Leaning Hanging Dressing Mirror Gold New - Refundable If Different Than Described and Only Before Item Leaves The Building. RETAIL $139.00 About this item Brand: Costway Manufacturer Part Number: QD-664-A83GD Color: Gold Product Weight: 22.5 lb Product Dimensions (L x W x H): 22.00 x 1.50 x 59.00 Inches Are you finding a full-length mirror for your bedroom or cloakroom? This stylish and functional mirror is perfect as a decorative element for any room in your house. This premium rectangle mirror is surrounded by an aluminum alloy frame and the large glass mirror is backed by MDF material for reinforcement and stability. Besides, the mirror is made of float glass to avoid distortion and equipped with an explosion-proof membrane to provide protection. Simple but elegant design increases the aesthetic feeling of the mirror and well-suited for home décor. Besides, it can be hanging or leaning according to your preference. Lot - 75 Queen Size Bed Frame with Button Tufted Wingback Headboard, Modern Upholstered Platform Bed, Strong Wooden Slats, No Box Spring Needed, Noise-Free, Easy Assembly, Dark Grey New - Refundable If Different Than Described and Only Before Item Leaves The Building. RETAIL $129.99 About this item Brand: Sismplly Size: Queen Product Dimensions: 83"L x 62.59"W x 42.5"H Special Feature: Squeak Resistant Color: Dark Grey Finish Type: Unfinished Material: Wood Style: Modern Maximum Weight Recommendation: 1000 Pounds Furniture Finish: Dark Grey Wingback Design: Bed frame queen size with headboard adding side wings can block light and noise, At the same time, it can also protect the wall from damage and enhance the stability and firmness of the entire bed Modern Upholstered Platform Bed: Exquisite button tufted wingback headboard, with high quality linen and high elastic sponge wrapped around the entire bed frame, various styles can be matched at will, exquisite and fashionable. Lot - 76 Wood Panels for Wall - Oak Acoustic Wall Panels - 4PK Wall Wood Panels - 94.49” x 12 - Soundproof Wood Wall Panels for Decor - Acoustic Slat Wood Wall Panels for Interior Decoration of Walls (Grey) New -. The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a

The Acoustic Mirror - Google Books

Brings much convenience while designing the combiner scheme.The proposed combiner has the following characteristics. First, the ultrasonic beam propagating path in this combiner is only in water. The ultrasonic beam does not transmit through any acoustic lens or other solid separators. It prevents the acoustic energy loss due to the acoustic impedance mismatching or the longitudinal-shear mode transforming at the liquid–solid interface. Therefore, this design guarantees low insertion loss. Second, the combiner achieves the acoustic focusing using the OPM, instead of acoustic lens. The OPM can provide a larger NA than the focused transducer. Therefore, the combiner has stronger acoustic focusing ability and better receiving sensitivity. Third, the ultrasonic beam is approximately collimated after being reflected by the OPM. It is convenient to settle a flat transducer or flat acoustic mirror in the combiner to redirect and receive the ultrasonic beam. Fourth, the combiner does not bring any additional optical element in the optical path, which promises low optical disorders. These characteristics would be useful in improving the performance of OR-PAM. 3.2. System PerformanceThe performance of the proposed optical-acoustic combiner was tested by phantom experiments. The experimental setup used for the performance test and imaging experiments is presented in Figure 1. The optical-acoustic confocal alignment was achieved before experiments. First, we carefully designed and customized the combiner and the parabolic mirror. The ultrasound transducer can be stably fixed in the combiner and the position of the acoustic focal spot can be approximately estimated according to the design. Second, by illuminating unfocused laser (not through the combiner) on a particle, we generated a point acoustic source. We could determine the position of the acoustic focal point, by adjusting the combiner in x, y, z direction until maximizing the received signal, which is similar to the experiments given in Figure 5. Third, we moved the acoustic focal spot to a black tape and adjust the position of the incident laser beam (through the combiner) until maximizing the receiving signal. Then, we can say that the confocal alignment is achieved.In the first experiment, we examined the ability of ultrasonic focusing of the combiner. The imaging target is a single polyester particle with a diameter of approximately 100 μm. We separated the single microsphere and then taped it on a cover glass. There was some interspace between the tape and the microsphere and we filled it with distilled water. Laser beam with a diameter approximately 5 mm was directly illuminating on the micro-particle from below, through a mirror under the target, but not through the combiner. Whereas, generated PA signals were detected through the ultrasonic transducer in the combiner. The combiner was moved by the 2D motorized translational stage. Then, images of the micro-particle

Fulwell Acoustic Mirror - northeastheritagelibrary.co.uk

The carbon fiber, indicated by the white arrow in (a). MAP: maximum amplitude projection. Figure 7. PA imaging of the brain vasculatures of a mouse through an intact skull. (a) The normalized MAP image of the brain vasculature. (b) The depth-encoded image of the brain vasculatures. The scale bar in the figure represents 1 mm. PA: photoacoustic. Figure 7. PA imaging of the brain vasculatures of a mouse through an intact skull. (a) The normalized MAP image of the brain vasculature. (b) The depth-encoded image of the brain vasculatures. The scale bar in the figure represents 1 mm. PA: photoacoustic. Figure 8. PA imaging of the iris of a live mouse. (a) The normalized MAP image of the iris. The eyelid around is also imaged. (b) The depth-encoded image of the iris and surrounding tissues. The scale bar (the white solid line) in the figure represents 500 μm. Figure 8. PA imaging of the iris of a live mouse. (a) The normalized MAP image of the iris. The eyelid around is also imaged. (b) The depth-encoded image of the iris and surrounding tissues. The scale bar (the white solid line) in the figure represents 500 μm. Table 1. The system specifications of the proposed OPM. Table 1. The system specifications of the proposed OPM. Off-Axis Distance [mm]Diameter of OPM [mm]RFL of OPM [mm]PFL of OPM [mm]616148.5 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( Share and Cite MDPI and ACS Style Zhang, X.; Liu, Y.; Tao, C.; Yin, J.; Hu, Z.; Yuan, S.; Liu, Q.; Liu, X. High-Sensitivity Optical-Resolution Photoacoustic Microscopy with an Optical-Acoustic Combiner Based on an Off-Axis Parabolic Acoustic Mirror. Photonics 2021, 8, 127. AMA Style Zhang X, Liu Y, Tao C, Yin J, Hu Z, Yuan S, Liu Q, Liu X. High-Sensitivity Optical-Resolution Photoacoustic Microscopy with an Optical-Acoustic Combiner Based on an Off-Axis Parabolic Acoustic Mirror. Photonics. 2021; 8(4):127. Chicago/Turabian Style Zhang, Xiang, Yang Liu, Chao Tao, Jie Yin, Zizhong Hu, Songtao Yuan, Qinghuai Liu, and Xiaojun Liu. 2021. "High-Sensitivity Optical-Resolution Photoacoustic Microscopy with an Optical-Acoustic Combiner Based on an Off-Axis Parabolic Acoustic Mirror" Photonics 8, no. 4: 127. APA Style Zhang, X., Liu, Y., Tao, C., Yin, J., Hu, Z., Yuan, S., Liu, Q., & Liu, X. (2021). High-Sensitivity Optical-Resolution Photoacoustic Microscopy with an Optical-Acoustic Combiner Based on an Off-Axis Parabolic Acoustic Mirror. Photonics, 8(4), 127. Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

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Yep.First, the sound moves from left to right, between the acoustic centers of the speakers. Since a speaker's acoustic center may not be its physical center, you should use the first Lateral test to adjust your speakers until the sound traverses a 60 degrees angle from the listener's point of view. Second, the sound moves from beyond the right loudspeaker to beyond the left (about 1' out from acoustic center). The next two signals are the mirror image of the above; third, from right to left speaker, and fourth, from beyond the left to beyond the right.Again, grade your system by how straight, continuous, and symmetrical this path is. Grade the beyond path by how far out from the speaker it appears to go (about 1' to the left or right of the requisite speaker, according to Doug Jones), and that it does not approach or recede from the listener.

Acoustic Mirror echoes of silence

Flat transducer combined with the OPM. Figure 3. Two kinds of acoustic focusing schemes. (a) A spherically-focused transducer combined with a flat acoustic reflector. (b) A flat transducer combined with the OPM. Figure 4. Simulation of acoustic focusing performance of the combiner. The amplitude of the acoustic field is normalized to the amplitude at the transducer surface. (a) Acoustic field near the focus of a spherically-focused transducer [the scheme in Figure 3a]. (b) Acoustic field near the focus of the proposed combiner [the scheme in Figure 3b]. (c) Comparison of the acoustic field along the axis, where L is 30 mm. (d) Normalized amplitude at the focus with various distance L, and L is the distance between the transducer and the mirror center. Figure 4. Simulation of acoustic focusing performance of the combiner. The amplitude of the acoustic field is normalized to the amplitude at the transducer surface. (a) Acoustic field near the focus of a spherically-focused transducer [the scheme in Figure 3a]. (b) Acoustic field near the focus of the proposed combiner [the scheme in Figure 3b]. (c) Comparison of the acoustic field along the axis, where L is 30 mm. (d) Normalized amplitude at the focus with various distance L, and L is the distance between the transducer and the mirror center. Figure 5. Measurement of acoustic field experiment of the combiner. (a) Five images around the focus. (b) Normalized acoustic pressure along the acoustic axis, where blue empty dots represent experiment results and the red solid line is the simulative data. (c) The image obtained on the focal plane. Two black dashed lines marked profiles at the focus along x direction and y direction. The white scale bar in the figure represents 200 μm. (d,e) Profiles along x direction and y direction in (c). Figure 5. Measurement of acoustic field experiment of the combiner. (a) Five images around the focus. (b) Normalized acoustic pressure along the acoustic axis, where blue empty dots represent experiment results and the red solid line is the simulative data. (c) The image obtained on the focal plane. Two black dashed lines marked profiles at the focus along x direction and y direction. The white scale bar in the figure represents 200 μm. (d,e) Profiles along x direction and y direction in (c). Figure 6. Imaging of the carbon fiber. (a) MAP image of the carbon fibers. The green dashed rectangle is the sampling region. (b) Profile along the x-direction of the carbon fiber, indicated by the white arrow in (a). MAP: maximum amplitude projection. Figure 6. Imaging of the carbon fiber. (a) MAP image of the carbon fibers. The green dashed rectangle is the sampling region. (b) Profile along the x-direction of. The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a

The Acoustic mirror by Like Mirror: The solution to isolate your

To achieve acoustic focusing. One was achieved by a spherically focused ultrasonic transducer and a flat acoustic reflector [28]. Another one was achieved by an unfocused transducer and the proposed combiner. The surface sensitivity of the transducer was set as the same with each other. The two transducers had the same element size of 12 mm and the same central frequency of 15 MHz. Moreover, the focuses were both fixed at the same position (14 mm below the central axis). During this process, the flat acoustic mirror and the focus remains stationary and the transducer’s position was adjusted along the central axis of the OPM to fix the focus at the same position. This meant that the focus was maintained 14 mm under the central axis. The distance L between the transducer and the mirror center was 10 to 30 mm in the following simulation. For the spherically focused transducer, its focal length varied from 24 mm to 44 mm, in order to keep consistent with the set position. The surrounding media is water, in which the speed of sound is 1500 m/s.Figure 4 compares the acoustic focusing performance of two schemes. Figure 4a illustrated the predicted detection sensitivity achieved by a spherically focused transducer and a flat acoustic reflector. Figure 4b gives the detection sensitivity achieved by the OPM with a flat transducer. It was seen that the focal spot achieved by the scheme one was much bigger than that achieved by the proposed scheme. Additionally, its focal intensity was much weaker than the proposed scheme, as shown in Figure 4c. It meant that the proposed method had stronger acoustic focusing ability. It was said that the proposed combiner has better receiving sensitivity than the scheme of the focused transducer and the flat acoustic reflector. This was because the proposed combiner had a larger acoustical NA, as shown in Figure 3.Additionally, we also predicted the situation when the transducer is far away from the reflector. For the scheme composed of a focused transducer and a flat acoustic reflector, the focal length must be increased in order to maintain the focal position. The results showed the sensitivity at the focus was decreased as the distance L was increased, as shown in Figure 4d with the solid dots. However, for the proposed combiner, as the transducer was far away from the OPM, the intensity at focus almost remained stable, even when the distance L was increased from 10 to 30 mm. This was because the ultrasonic beam excited from the focus of the OPM was reflected and redirected into a collimated beam. The collimated beam meant that the receiving transducer could be placed at any position of the central axis, which

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Author / Affiliation / Email Article Menu Font Type: Arial Georgia Verdana Open AccessMore Editor’s choice articles in journal Photonics.">Editor’s ChoiceArticle by Xiang Zhang 1,†, Yang Liu 1,†, Chao Tao 1,*, Jie Yin 2, Zizhong Hu 3, Songtao Yuan 3,*, Qinghuai Liu 3 and Xiaojun Liu 1,* 1 Ministry-of-Education Key Laboratory of Modern Acoustics, Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China 2 Nanjing Polytechnic Institute, Nanjing 210048, China 3 Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China * Authors to whom correspondence should be addressed. † These authors contributed equally to this work. Submission received: 23 March 2021 / Revised: 8 April 2021 / Accepted: 14 April 2021 / Published: 18 April 2021 Abstract: Optical-resolution photoacoustic microscopy (OR-PAM) is a promising noninvasive biomedical imaging technology with label-free optical absorption contrasts. Performance of OR-PAM is usually closely related to the optical-acoustic combiner. In this study, we propose an optical-acoustic combiner based on a flat acoustic reflector and an off-axis parabolic acoustic mirror with a conical bore. Quantitative simulation and experiments demonstrated that this combiner can provide better acoustic focusing performance and detection sensitivity. Moreover, OR-PAM is based on the combiner suffer low optical disorders, which guarantees the good resolution. In vivo experiments of the mouse brain and the iris were also conducted to show the practicability of the combiner in biomedicine. This proposed optical-acoustic combiner realizes a high-quality optical-acoustic confocal alignment with minimal optical disorders and acoustic insertion loss, strong acoustic focusing, and easy implementation. These characteristics might be useful for improving the performance of OR-PAM. 1. IntroductionPhotoacoustic (PAI) imaging is a promising noninvasive biomedical imaging technology and has been rapidly developed in recent years [1,2,3,4,5,6,7,8]. Optical-resolution photoacoustic microscopy (OR-PAM) is one form of the PAI inheriting its characteristics and is useful in both preclinical and clinical research [9]. In OR-PAM, the tissue is irradiated usually by a focused short-pulsed laser beam to achieve a thermal and acoustic impulse response, which is called the photoacoustic (PA) effect [10,11,12]. PA wave is received by the ultrasonic transducer, and transferred into a computer to form the images of the tissues. OR-PAM could achieve images with a resolution of micron-scale or even submicron-scale level and a penetration depth of up to one millimeter [13]. Moreover, it is unique among optical microscopy technologies for its label-free detection of optical absorption with a relative sensitivity of 100% [14]. Hence, OR-PAM has shown great potentials in various biomedical applications, such as brain imaging [2,5,15,16], breast cancer imaging [3], animal embryo imaging [4,17], cell imaging [18,19,20], and microcirculation imaging [6,21,22,23,24,25,26,27,28,29,30].Usually, an OR-PAM system involves an optical-acoustic combiner to achieve the optical-acoustic confocal alignment. An early. The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a Download Mirrors (Acoustic) - Beth MP3 song on Boomplay and listen Mirrors (Acoustic) - Beth offline with lyrics. Mirrors (Acoustic) - Beth MP3 song from the Beth’s album Mirrors (Acoustic) is released in 2025.

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(12 miles) further to the south as the crow flies but the drive covers twice the distance thanks to the need to cross the Tees at Middlesborough.Boulby mirror with its hollow (Photo: Alun Taylor)The mirror sits amid a modern housing estate, on the corner of Greenstone Road and Holyhead Drive. A plaque at the site states that it was built in 1916 by the Royal Engineers. In size and shape the Redcar mirror is very similar to that at Fulwell and here again the stand for the acoustic receiver has survived.The surrounding housing estate has robbed the site of its geographical context, though. Originally it commanded an uninterrupted view of the North Sea.A further 19.31km (12 miles) east sits the Boulby Mirror from which – on a fine day – there are spectacular views over the North Sea and the Cleveland Way footpath. On the day I visited a fog bank rolled in that cut visibility down to 20m (65.61ft).The mirror is situated on privately owned farm land, the farmhouse being immediately next to the mirror heading west.Talking to the farm owner, I discovered they have a pretty steady stream of visitors asking for permission to hop over the gate and take a shufti. They could not have been more accommodating so please ask before you enter the field.J R V Carter reported in the Yorkshire Archaeological Journal Vol. 61 for 1989 that the Boulby mirror was also built in 1916. The mirror is set some 500m (1,640.42ft) back from the cliff edge to reduce the interference from wave noise and faces NNE to cover the approaches to the Tees estuary.More than a century of wear chips away at BoulbyLike Fulwell and Redcar, the Boulby mirror is a listed Grade II structure, but – unlike Fulwell and Redcar – there is no plaque and the mirror has undergone no restoration. The concrete rendering is flaking off, giving a view of the underlying concrete cast and corrugated-iron shuttering.The Historic England description of the structure speculates that two small protrusions above the mirror may been used to mount microphones at some point.Unique