Taine Hollis is thirty six and he carries a sound level meter in a hard case, an acoustic calibrator in a pouch, a dosimeter in his other pocket, and a pen. He has been measuring other people's noise for eleven years and he has never once been asked to be quiet himself. The job in Ashburton was a renewal. Haldon Engineering build tipper bodies and hay handlers in a shed that started as a dairy implement workshop in 1961, and a licence renewal had come up and the health and safety people had asked for a noise control plan and a noise map. The limit in this country is a flat eighty five decibels on the A scale, averaged over the eight hour day, with a peak limit of a hundred and thirty seven on the C scale, and there is no swapping hours for decibels the way there is in some other countries. Eighty five is eighty five all day long.

Haldon had done the sensible things first. They had a plan, they had zones on the wall, they had ear defenders in a cupboard by the time clock, and the zones were painted by a sign writer who had gone by the office furniture and made them green, yellow and red out of the colours that were on the wall. Taine had seen that trick in four other workshops in Canterbury and he had said, before he had his meter out, that he would need to know where the numbers were before he could say anything about the colours. He checked the meter against the acoustic calibrator before he set out and he checked it again at the end of every day, and he wrote both readings in the front of the book. A meter that is a decibel and a half out will not tell anybody anything, and the whole profession is built on the assumption that somebody checked.

He walked the floor on a grid two metres square with the meter on a tripod at one and four tenths of a metre, which is roughly where a head sits, and he wrote the reading down in a column for each square. He used the fast time weighting, because he was moving about and had not yet thought to stay still. The office at the front was fifty two. The paint booth was fifty five. The yard at the roller door was sixty eight. The weld bay was seventy nine. The gas and gear store was seventy four. The extraction side of the saw bench was eighty eight. The compressor room was eighty six. The panel beat was ninety one. The press brake was eighty four.

He marked the panel beat red, the saw bench and the compressor room amber, and everything else green, and he wrote that ear defenders were required in the red zone and available on request elsewhere, and he wrote the fix list as a new canopy on the compressor intake and a new bearing for the extraction fan. Sinclair Raupo, the general manager, fifty two years old, read it with his glasses down his nose and said the total for the two items was eleven thousand dollars and asked whether the shop would still make money at the end of it. “The plan says the paint booth is quieter than the office,” Sinclair said. “How does that happen?” “It happens because it is a booth with glass in it and it takes forty minutes to change a job.”

Emery Slade was nineteen and in his second year and he swept the floor and ran the saw when the order book was thin. He had been the only person in the building willing to say what he thought, which is not unusual, because nobody else has anything to gain by saying it. “That’s not the loud bit,” Emery said, on the second afternoon, when Taine was standing over the panel beat. “The loud bit is when the saw starts and the fan comes up.” “Your saw is the loudest thing in here.” “No it isn’t. It’s loud for a second and then the fan comes on and the fan stays on.” They stood at the edge of the saw bench and listened to it happen, and it happened the way Emery said it would. The saw itself ran for eleven seconds at eighty eight. Then the extraction fan came up to speed over about four seconds and the room filled with something that was not loud and was everywhere.

On the Friday, Taine was set up at the press brake to work out how the machine's own noise and the room's noise combine, because that number was going to be in the report and he was not going to put a number in a report that he had not made himself. He measured the press on its own at eighty four at the operator's position. He measured the extraction running at the same place at seventy nine. He wrote both on the back of a sheet, and then he added them, because that is what the number wanted to be, and he wrote one hundred and sixty three. He looked at it for a while. “That’s not a noise,” he said. Emery looked over his shoulder. “That’s a big noise.” “It’s not a noise at all. It’s arithmetic.” He turned the sheet round. “Eighty four and seventy nine make eighty five point two. They don’t make a hundred and sixty three. Two noises make one noise and the one noise is barely above the louder of the two.” “How do you get eighty five point two?”

“By working in the bottom of the number instead of the top of it.” He wrote it out. Sound is counted as a pressure and a pressure of double the size is six decibels more. So a decibel is not a slice of loudness you can add, it is a ruler laid over a staircase. Two staircases merge into one staircase. Eighty and eighty becomes eighty three. Seventy four and seventy four becomes seventy seven. Emery read that twice. “So when they say the press is eighty four and the extractor is seventy nine, the room is eighty five point two.” “The room is eighty five point two.” “And nobody can turn either one off to hear the other one.”

He opened the cupboard by the time clock while he was standing there anyway. There were three boxes of defenders on the shelf and the defenders were rated SLC 75, which is the way they are rated here and which everybody in the trade reads as a subtraction. It is not a subtraction. It is a proportion of the sound energy that gets through, and three quarters blocked is six decibels, not twenty six. A shopkeeper who tells a man his defenders take twenty six decibels is promising him four times what the box in his hand will do, and a man who works out that way stops trusting the number that is actually on the machine.

The report went in on the eleventh of August. It was a good report. It had a plan, a map with the colours on it, a list of protectors with their ratings, and a table of what each machine was worth at the operator's ear. The table was wrong. The saw and the press brake both had spec sheets on the manufacturer's website. The saw was quoted at eighty two decibels of sound power. Taine needed sound pressure at an operator's ear, and sound power does not change with distance while sound pressure halves in strength every time you double the distance and loses six decibels doing it. He had read the eighty two as though it were a pressure reading at one metre. From one metre to the operator's position at three hundred millimetres he had taken off three decibels, and he had written seventy nine in the table for the saw.

The press brake had no sound power figure at all, so he had built one out of the brochure and the distance rule and the assumption that the machine in the photograph was the machine in the shed. He put the press brake operator position at seventy one. Both figures were defensible on paper and both were fiction. The saw bench measured eighty eight at the operator's ear and he had told Sinclair Raupo it was seventy nine. The press brake measured eighty four at the grid point he had chosen, which was two metres out on the walkway, and he had told Sinclair Raupo it was seventy one at the operator's position.

Denise Riddell was forty seven and had stood at the press brake for twenty two years. She did her annual audiogram in the following March in a soundproof booth in Ashburton with headphones on and a technician who did not talk. Both her ears came back with a dip at three kilohertz, which is the shape that noise makes when it has been made at that frequency for that long, and the technician explained it to her in a sentence she has repeated to everybody since. Her hearing aid claim went to her insurer, and the insurer sent it to a hygienist of their own, and the hygienist came out and measured the press brake bay properly and got an eight hour figure of ninety one decibels, and he found her employer's copy of Taine's report and used the table in it, because the table said the operator's position was seventy one and seventy one is not an accident anybody can have.

The claim was reduced on the grounds that the employer could not reasonably have been expected to protect against a hazard their own paid assessment had reported as safe. Denise Riddell was re-roled onto the stores desk in July. She kept her pay and she lost the job she had done for twenty two years, and she bought a hearing aid in September out of her own pocket, and the case notes say the assessment had been done properly and thoroughly.

Taine went back to Ashburton in August and did it the way it should be done, and it took eleven days instead of two. He logged. He left a meter integrating for the whole shift at each of the eleven work positions somebody actually occupied, not the positions on a grid. He ran two meters at once, one fixed as a reference and one moving, so that every reading could be compared with the same reference at the same minute. He ran the shop after hours, lights off, plant off, to find out what the room was when nothing was happening in it, and that came to fifty four decibels with the door shut and forty one with it open. The floor of the shop with the plant running and the saw off was seventy four. Seventy four decibels for a room in which nothing was happening. He had measured it eleven times over four days and it did not vary by more than one.

The positions told a different map. Panel beat, eighty seven over the day, because the panel beater pushes steel for three hours and does paperwork for five. Saw bench, eighty six, because the saw runs hard for five and a half hours and the extraction runs for eight. Press brake, ninety one, because the operator stands in a bay one point two metres wide with her head three hundred millimetres from the guard rail and the hydraulic pump on that machine screaming at her from under the bench. He had measured the press brake from two metres away on a walkway. The operator's head was not on the walkway. He had put his own meter where it was convenient to stand and had written a number for a place where nobody stands, and the place where Denise Riddell stood was nine decibels above it.

Emery was right about the fan. He put the meter inside the extraction duct and outside it and the duct carried ninety three at two hundred and fifty hertz. The A scale takes about nine decibels off two hundred and fifty hertz, which is why a meter on the A scale understates a noise that is mostly low, and he repeated the whole map on the C scale where the weighting is flat and the saw bench came up four decibels against the office, which is what a low frequency noise does to a room.

The seventy four was the last thing and it was the cheapest thing. He put the ultrasound probe down on the floor by the compressor room and walked it along the ring main, and the probe screamed at one place, a forty millimetre drain cock on the hundred and fifty millimetre ring main that had a gland nut worn so it had been weeping very slightly since somebody closed it hard in 2018. He held a twenty litre plastic bag over it and filled it and timed it on his phone. Twenty litres in three point six seconds. Twenty cubic metres an hour of hot compressed air going into the room from the floor. He closed the ring main's isolation valve and the floor of the shop went from seventy four to sixty nine. The compressor meter said the shop was drawing four hundred and thirty four cubic metres an hour on a Wednesday and four hundred and fourteen on a Friday. The machine makes four hundred and fourteen. The extra twenty was the floor.

The other twenty was the compressor's intake silencer, which had a canopy over it until 2018 when a partition wall was moved and the canopy was taken off to get a pallet through, and which had been running for six years without one. He stood at eight metres from the intake and measured eighty four. He put his hand on it and it vibrated. The canopy came from Christchurch for three thousand eight hundred dollars installed. The gland nut, a washer and a nipple cost forty one dollars. The plant room floor went from seventy four to sixty six.

The second report went in on the fourth of October, eight pages, with the original one withdrawn and a covering note that said why. It had eleven position figures instead of a grid of spot readings, a table that said what each contribution was worth at each ear, and a fix list in the order Sinclair Raupo could afford it. A seat platform for the press brake operator, four hundred millimetres high, so her head comes up out of the hot air and away from the pump by nine hundred millimetres, three thousand four hundred dollars. The pump rebuilt, nineteen thousand. A local extraction hood at the saw bench, six thousand two hundred. The canopy, three thousand eight hundred. The washer, forty one.

The platform bought three decibels. She was at eighty eight. The pump bought five and a half and she was at eighty two point five and under the limit, and she is still on the press brake, and the noise control plan has been rewritten twice since and Haldon still runs the saw bench at eighty four point six because the fan bearings and the hood and the twenty metre of duct the same company wanted to rebuild for a hundred and eighty thousand dollars turned out to be worth less than three thousand dollars of careful attention. Denise Riddell's claim was reopened in November on the strength of the second report and paid in February, and the insurer wrote to Sinclair Raupo and told him to look at his own paperwork more carefully. Emery Slade was twenty that November and had said one true thing on a Tuesday afternoon and had been listened to.

Taine went up to Ashburton one more morning in December, before the shop opened, to put the meter on the tripod in the press brake bay and let it log the whole first hour while the shop was still being set up. The map on the table behind him was a grid of two metre squares in three colours, which is how a map of a floor gets made, because two metre squares are easy to walk with a tape and easy to draw and easy to divide up between two people. Every square on it held one number, and the number was the average of everywhere inside it, and everywhere inside a two metre square is not one place. He wrote the date and the serial number of the meter and the date the calibrator was last checked on the front of the log sheet, and then he wrote the hour's figure, which was eighty two point four, and then he put the pen down and left the meter running to log the day behind it. The shop filled up around him. Somebody opened the roller door and the yard came in at sixty eight and stayed underneath everything else, the way it always does.