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  "title" : "environmentalSoundReduction"
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# environmentalSoundReduction

A quantity sample type that measures the difference in sound intensity when wearing headphones that lower environmental sound levels.

```
static let environmentalSoundReduction: HKQuantityTypeIdentifier
```

## Discussion

These samples use sound pressure units (described in [`HKUnit`](/documentation/HealthKit/HKUnit)). They measure discrete values of the equivalent continuous sound pressure level, described in [`HKQuantityAggregationStyle.discreteEquivalentContinuousLevel`](/documentation/HealthKit/HKQuantityAggregationStyle/discreteEquivalentContinuousLevel). Environmental sound reduction values are automatically collected when wearing supported headphones.

---

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