This component was made to measure environmental noise levels (Leq, Lmin, Lmax, Lpeak) with different frequency weightings over configured time intervals. It is heavily based on awesome work by Ivan Kostoski: esp32-i2s-slm (his hackaday.io project).
Typical weekly traffic noise recorded with a microphone located 50m from a medium traffic road:
Add it to your ESPHome config:
external_components:
- source: github://stas-sl/esphome-sound-level-meter # add @tag if you want to use a specific version (e.g @v1.0.0)For configuration options see minimal-example-config.yaml or advanced-example-config.yaml:
i2s:
bck_pin: 23
ws_pin: 18
din_pin: 19
sample_rate: 48000 # default: 48000
bits_per_sample: 32 # default: 32
dma_buf_count: 8 # default: 8
dma_buf_len: 256 # default: 256
use_apll: true # default: false
# according to datasheet when L/R pin is connected to GND,
# the mic should output its signal in the left channel,
# however in my experience it's the opposite: when I connect
# L/R to GND then the signal is in the right channel
channel: right # default: right
# right shift samples.
# for example if mic has 24 bit resolution, and
# i2s configured as 32 bits, then audio data will be aligned left (MSB)
# and LSB will be padded with zeros, so you might want to shift them right by 8 bits
bits_shift: 8 # default: 0
sound_level_meter:
id: sound_level_meter1
# update_interval specifies over which interval to aggregate audio data
# you can specify default update_interval on top level, but you can also override
# it further by specifying it on sensor level
update_interval: 60s # default: 60s
# you can disable (turn off) component by default (on boot)
# and turn it on later when needed via sound_level_meter.turn_on/toggle actions;
# when used with switch it might conflict/being overriden by
# switch state restoration logic, so you have to either disable it in
# switch config and then is_on property here will have effect,
# or completely rely on switch state restoration/initialization and
# any value set here will be ignored
is_on: true # default: true
# buffer_size is in samples (not bytes), so for float data type
# number of bytes will be buffer_size * 4
buffer_size: 1024 # default: 1024
# ignore audio data at startup for this long
warmup_interval: 500ms # default: 500ms
# audio processing runs in a separate task, you can change its settings below
task_stack_size: 4096 # default: 4096
task_priority: 2 # default: 2
task_core: 1 # default: 1
# see your mic datasheet to find sensitivity and reference SPL.
# those are used to convert dB FS to db SPL
mic_sensitivity: -26dB # default: empty
mic_sensitivity_ref: 94dB # default: empty
# additional offset if needed
offset: 0dB # default: empty
# for flexibility sensors are organized hierarchically into groups. each group
# could have any number of filters, sensors and nested groups.
# for examples if there is a top level group A with filter A and nested group B
# with filter B, then for sensors inside group B filters A and then B will be
# applied:
# groups:
# # group A
# - filters:
# - filter A
# groups:
# # group B
# - filters:
# - filter B
# sensors:
# - sensor X
groups:
# group 1 (mic eq)
- filters:
# for now only SOS filter type is supported, see math/filter-design.ipynb
# to learn how to create or convert other filter types to SOS
- type: sos
coeffs:
# INMP441:
# b0 b1 b2 a1 a2
- [ 1.0019784 , -1.9908513 , 0.9889158 , -1.9951786 , 0.99518436]
# nested groups
groups:
# group 1.1 (no weighting)
- sensors:
# 'eq' type sensor calculates Leq (average) sound level over specified period
- type: eq
name: LZeq_1s
id: LZeq_1s
# you can override updated_interval specified on top level
# individually per each sensor
update_interval: 1s
# you can have as many sensors of same type, but with different
# other parameters (e.g. update_interval) as needed
- type: eq
name: LZeq_1min
id: LZeq_1min
unit_of_measurement: dBZ
# 'max' sensor type calculates Lmax with specified window_size.
# for example, if update_interval is 60s and window_size is 1s
# then it will calculate 60 Leq values for each second of audio data
# and the result will be max of them
- type: max
name: LZmax_1s_1min
id: LZmax_1s_1min
window_size: 1s
unit_of_measurement: dBZ
# same as 'max', but 'min'
- type: min
name: LZmin_1s_1min
id: LZmin_1s_1min
window_size: 1s
unit_of_measurement: dBZ
# it finds max single sample over whole update_interval
- type: peak
name: LZpeak_1min
id: LZpeak_1min
unit_of_measurement: dBZ
# group 1.2 (A-weighting)
- filters:
# for now only SOS filter type is supported, see math/filter-design.ipynb
# to learn how to create or convert other filter types to SOS
- type: sos
coeffs:
# A-weighting:
# b0 b1 b2 a1 a2
- [ 0.16999495 , 0.741029 , 0.52548885 , -0.11321865 , -0.056549273]
- [ 1. , -2.00027 , 1.0002706 , -0.03433284 , -0.79215795 ]
- [ 1. , -0.709303 , -0.29071867 , -1.9822421 , 0.9822986 ]
sensors:
- type: eq
name: LAeq_1min
id: LAeq_1min
unit_of_measurement: dBA
- type: max
name: LAmax_1s_1min
id: LAmax_1s_1min
window_size: 1s
unit_of_measurement: dBA
- type: min
name: LAmin_1s_1min
id: LAmin_1s_1min
window_size: 1s
unit_of_measurement: dBA
- type: peak
name: LApeak_1min
id: LApeak_1min
unit_of_measurement: dBA
# group 1.3 (C-weighting)
- filters:
# for now only SOS filter type is supported, see math/filter-design.ipynb
# to learn how to create or convert other filter types to SOS
- type: sos
coeffs:
# C-weighting:
# b0 b1 b2 a1 a2
- [-0.49651518 , -0.12296628 , -0.0076134163, -0.37165618 , 0.03453208 ]
- [ 1. , 1.3294908 , 0.44188643 , 1.2312505 , 0.37899444 ]
- [ 1. , -2. , 1. , -1.9946145 , 0.9946217 ]
sensors:
- type: eq
name: LCeq_1min
id: LCeq_1min
unit_of_measurement: dBC
- type: max
name: LCmax_1s_1min
id: LCmax_1s_1min
window_size: 1s
unit_of_measurement: dBC
- type: min
name: LCmin_1s_1min
id: LCmin_1s_1min
window_size: 1s
unit_of_measurement: dBC
- type: peak
name: LCpeak_1min
id: LCpeak_1min
unit_of_measurement: dBC
# automation
# available actions:
# - sound_level_meter.turn_on
# - sound_level_meter.turn_off
# - sound_level_meter.toggle
switch:
- platform: template
name: "Sound Level Meter Switch"
# if you want is_on property on component to have effect, then set
# restore_mode to DISABLED, or alternatively you can use other modes
# (more on them in esphome docs), then is_on property on the component will
# be overriden by the switch
restore_mode: DISABLED # ALWAYS_OFF | ALWAYS_ON | RESTORE_DEFAULT_OFF | RESTORE_DEFAULT_ON
lambda: |-
return id(sound_level_meter1).is_on();
turn_on_action:
- sound_level_meter.turn_on
turn_off_action:
- sound_level_meter.turn_off
button:
- platform: template
name: "Sound Level Meter Toggle Button"
on_press:
- sound_level_meter.toggle: sound_level_meter1
binary_sensor:
- platform: gpio
pin: GPIO0
name: "Sound Level Meter GPIO Toggle"
on_press:
- sound_level_meter.toggle: sound_level_meter1Check out filter-design notebook to learn how those SOS coefficients were calculated.
In Ivan's project SOS filters are implemented using ESP32 assembler, so they are really fast. A quote from him:
Well, now you can lower the frequency of ESP32 down to 80MHz (i.e. for battery operation) and filtering and summation of I2S data will still take less than 15% of single core processing time. At 240MHz, filtering 1/8sec worth of samples with 2 x 6th-order IIR filters takes less than 5ms.
I'm not so familiar with assembler and it is hard to understand and maintain, so I implemented filtering in regular C++. Looks like the performance is not that bad. At 80MHz filtering and summation takes ~210ms per 1s of audio (48000 samples), which is 21% of single core processing time (vs. 15% if implemented in ASM). At 240MHz same task takes 67ms (vs. 5x8=40ms in ASM).
| CPU Freq | # SOS | Sensors | Sample Rate | Buffer size | Time (per 1s audio) |
|---|---|---|---|---|---|
| 80MHz | 0 | 1 Leq | 48000 | 1024 | 57 ms |
| 80MHz | 6 | 1 Leq | 48000 | 1024 | 204 ms |
| 80MHz | 6 | 1 Lmax | 48000 | 1024 | 211 ms |
| 80MHz | 6 | 1 Lpeak | 48000 | 1024 | 207 ms |
| 240MHz | 0 | 1 Leq | 48000 | 1024 | 18 ms |
| 240MHz | 6 | 1 Leq | 48000 | 1024 | 67 ms |
| 240MHz | 6 | 1 Leq, 1 Lpeak, 1 Lmax, 1 Lmin | 48000 | 1024 | 90 ms |
Tested with ESPHome version 2024.9.0, platforms:
- ESP32 (Arduino v2.0.6, ESP-IDF v4.4.5)
- ESP32-IDF (ESP-IDF v4.4.7)
See sensor-community-example-config.yaml
- ESP32-I2S-SLM hackaday.io project
- Measuring Audible Noise in Real-Time hackaday.io project
- What are LAeq and LAFmax?
- Noise measuring @ smartcitizen.me
- EspAudioSensor
- Design of a digital A-weighting filter with arbitrary sample rate (dsp.stackexchange.com)
- How to compute dBFS? (dsp.stackexchange.com)
- Microphone Specification Explained
- esp32-i2s-slm source code
- DNMS source code
- NoiseLevel source code
