Astley Business Park: the noise report predicted 36 dB. We measured 61 dB.

Murray Acoustics has carried out an independent operational noise survey at Astley Business Park, Astley Park Way, Tyldesley, on behalf of the Astley Warehouse Action Group. This update compares the night-time noise levels predicted in the noise assessment that supported planning permission A/23/96226/MAJOR with the levels measured on site in July 2026.

At 38 Withington Drive, the closest and worst affected dwelling assessed, the approved assessment predicted a night-time maximum level of 51 dB at the first-floor bedroom windows. Levels derived from measurement at that same position are 71 dB.

What the approved assessment predicted

The permission is supported by Tetra Tech report 784-B034505 Revision 7, dated 13 May 2024. That revision is the one referred to in Condition 4 of the decision notice.

It adopts an internal criterion of 45 dB LAmax in bedrooms at night, taken from the World Health Organisation’s Guidelines for Community Noise 1999. That is the level below which individual noise events are considered unlikely to disturb sleep.

The report states a 10 dB reduction through an open window. Every table uses a more favourable 15 dB. Those 5 dB are the difference between pass and fail.

The night-time predictions are given at a receptor height of 4.0 m, representing first-floor bedroom windows. At that position the report predicts 51 dB LAmax externally with the acoustic barriers secured by Condition 4 in place, and 36 dB LAmax inside the bedroom with the window partially open, some 9 dB below its own criterion.

A departure from BS 4142

BS 4142:2014+A1:2019 is the standard conventionally used to assess sound of an industrial or commercial nature against the prevailing background sound level. Its scope expressly includes sound from the loading and unloading of goods at industrial and commercial premises, and from mobile plant and vehicles forming an intrinsic part of the sound emanating from the premises.

BS 4142 is the standard for assessing industrial noise affecting residential areas.

The approved assessment applies BS 4142 to the proposed building services plant. It does not apply the standard to the service yard, docking and heavy goods vehicle activity, which is the dominant source of noise from the development at night. No reason for the distinction is given in the report.

Had the standard been applied to the yard activity, the approved assessment’s own figures indicate that a significant adverse impact would have been the likely outcome. Its Table 6.2 predicts an external night-time level of 44.8 dB LAeq at that receptor; its Table 5.2 adopts a night-time background sound level of 34 dB LA90 at the same receptor. The excess over background is therefore around +11 dB before any correction for acoustic features, and BS 4142 indicates that a difference of around +10 dB is likely to be an indication of a significant adverse impact.

No reason for the deviation from BS 4142 is given in the report, and none is recorded on the file for why the Council accepted it.

That figure takes no account of the character of the source. Reversing alarms are tonal and intermittent, and dock and trailer impacts are impulsive. Each would attract a correction under Section 11 of the standard, raising the rating level further.

What we measured

Continuous unattended measurements were undertaken between 27 and 29 July 2026 using a Class 1 sound level meter, at a position within the curtilage of the dwelling and at a microphone height of 2.5 m. Calibration was verified before and after use. Audio recordings were triggered alongside the logged data so that individual events could be identified.

Night-time maximum levels attributable to operations at the site reach 68 dB LAFmax at that position. The measurement position is not the assessed receptor position: it sits nearer the boundary barrier and lower than the first-floor bedroom windows, where the barrier screens less effectively. The measured level therefore understates what reaches the bedrooms.

Modelling the difference

A three-dimensional acoustic model of the site and the surrounding residential area was constructed in CadnaA, using the site geometry, building heights and boundary mitigation of the approved assessment. Two scenarios were run. Scenario A applies the source data of the approved assessment. Scenario B applies source levels calibrated to the levels measured in July 2026. Every other input is identical, so the difference between the two is attributable solely to the source terms.

Same model. Same houses. Same barriers. The only thing that changed is how loud the site actually is.

The comparison

At 38 Withington Drive, the levels derived from measurement are approximately 20 dB above the predicted external level, and 25 dB above the internal level predicted in the approved assessment. The decibel scale is logarithmic, and an increase of 10 dB is generally perceived as a doubling of loudness, so a difference of this order represents individual events several times as loud as those predicted.

61 dB in a bedroom at night. Likely to be perceived as five times as loud as predicted during the planning process.

The predicted internal level applies the 15 dB open-window reduction used in the report’s assessment tables; the measured internal level applies the 10 dB reduction stated in its method. On a consistent 15 dB basis the measured internal level is 56 dB, and the difference 20 dB. On either basis it exceeds the 45 dB criterion the approved assessment adopted for itself.

Conclusion

The contour comparison indicates that the difference is not confined to the worst affected dwelling, and extends across the first row of properties on Withington Drive.

The dominant source of night-time noise from the development was not assessed against BS 4142. On the approved assessment’s own predicted level, and its own adopted background sound level, such an assessment would have indicated a likely significant adverse impact before any correction for the character of the source.

These findings are preliminary and are issued in advance of the full survey report. They are, in the opinion of Murray Acoustics Ltd, sufficient to warrant a full assessment of operational noise from the site to BS 4142, together with measured verification of the mitigation secured by Condition 4 of the planning permission.