The Tale of Sonora Taro ~The Day a Soundproofing Wall Made the Noise Louder~

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This happened 11 years ago. Sonora Taro was called out to a scrap yard affiliated with a certain ironworks company. “We’ve been getting noise complaints from the residents,” they told him. Hearing this, Sonora Taro inspected the site, measured the sound levels, and submitted an estimate for noise reduction measures.

What he proposed was an L-shaped soundproofing wall. Sound doesn’t just travel in a straight line; it reflects, wraps around objects, and looks for an escape route. By using an L-shape, the sound was prevented from echoing, and the surroundings became quiet. Once the construction was finished, the area became properly quiet, and the client was overjoyed. Sonora Taro breathed a sigh of relief, thinking “Thank goodness,” and headed home with peace of mind.

Some time passed after that. Through an introduction from that same ironworks company, Sonora Taro visited a different scrap yard. There, looking extremely troubled, they shared this story with him:

“We had a local carpenter build a soundproofing wall for us. It’s made of 150mm thick ALC (Autoclaved Lightweight Concrete), 6 meters high, and 120 meters long. The bottom 2 meters from the ground were left completely open. Since there was already a concrete block wall there, I think they figured a wall at the lower level wasn’t necessary. This cost us 30 million yen. But… Something isn’t right. Even though we built the wall, it hasn’t gotten quiet at all. On the contrary, we’ve received complaints from the residents again, saying, ‘It’s so loud we can’t sleep!'”

Sonora Taro took one look at the site and immediately realized what was happening. The wall wasn’t providing any soundproofing effect whatsoever. On the contrary, the new soundproofing wall was acting as a reflective surface. The sound was bouncing off it and hitting the factory wall, actually amplifying the volume. The gap between the new wall and the factory wall was a mere 1 to 2 meters. With nowhere to escape, the sound was trapped, bouncing back and forth and growing louder and louder.

He was told that the carpenter who built the wall had shown the client the sound insulation performance data for the ALC material itself. It claimed a “40dB sound insulation effect.” Seeing that, the client had completely believed it. However, that data was strictly from lab tests. Numbers from lab measurements tend to skew excessively in an “optimistic” direction. Sonora Taro couldn’t help but mutter to himself, “Well, of course the standalone material data is going to say it blocks 40dB…”

Furthermore, the carpenter had not provided any “guarantee of the actual soundproofing effect.” The noise hadn’t diminished. In fact, it had gotten louder. And despite all this, the client was unable to get a refund for the massive sum of 30 million yen.

Sonora Taro decided to start by taking measurements. He used an instrument capable of measuring the sound at the property line and inside the factory simultaneously. The results were: Property Line: 61dB Sudden Noises: Over 100dB

According to the regulations, the noise level at the property line had to be kept at 55dB or lower. So, Sonora Taro proposed using [SHINOBI FABRIC]. He suggested this because trying to solve the problem using only rigid sound insulation panels would make the cost prohibitively expensive. Then, he stated clearly and confidently: “I guarantee that if we install this on the inside of the soundproofing wall and inside the factory, the noise level will drop to 55dB or less!”

The scrap yard owner was filled with anxiety. “What if I pay a huge amount of money again, only to make the exact same mistake…?” Driven by worry, they apparently reached out to a certain “Professor” for advice. And the “Professor” told them: “It’ll probably only drop by about 3dB or so. There’s no point in doing that.”

Hearing this, Sonora Taro firmly pushed back. “You can’t achieve proper noise control with sound insulation alone. Sound Absorption + Sound Insulation = Soundproofing!”

Even so, the scrap yard owner remained highly skeptical. So, Sonora Taro told them, “Let me show you a test so you can see it for yourself.”

First, he installed [SHINOBI FABRIC] over a 2-meter area. And sure enough, that specific section became noticeably quieter. “…” Since they still seemed anxious, he next tested a larger area of about 9 meters by 10 meters. The results were excellent. “If we expand the coverage, it will get even quieter!”

Yet, the client still wasn’t completely convinced. That’s when Sonora Taro offered another idea. “I’ve actually implemented this exact same solution at an ironworks in Chigasaki before. Please, go and see it for yourself.”

When the scrap yard owner visited the site in Chigasaki, the ironworks owner told him with a big smile: “It got so much quieter! Complaints? We don’t get those anymore!” “…I think I can trust him.” The scrap yard owner finally made his decision. Sonora Taro put his heart and soul into the project to ensure the client’s peace of mind.

Once the construction was completed, they measured the noise levels at the property line— “We did it!” The noise level had dropped below 55dB at the property line, even at its peak. Overall, the noise had been reduced by an impressive 20dB. To ensure the results weren’t being skewed by the sound of passing cars, they conducted simultaneous two-point measurements, definitively proving that the problem was fully resolved.

From the very day the final report was submitted and the construction wrapped up, the complaints from the residents completely stopped. The top executives from the ironworks company came in droves to see the results for themselves. The third-party measurements also cleared every single standard perfectly.

To see the joyful faces of his clients, Sonora Taro continues to face the challenge of sound today. Sound: If you measure it correctly, analyze it correctly, and implement the correct measures, it will always quiet down.

Today, once again, Sonora Taro is making the Earth just a little bit quieter.