Is a larger more powerful motor likely to be louder or quieter (cooker hoods)?

[DIYNotIan]

Hi

I'm looking at getting a new cooker hood. Like most people I guess, I want it to be as effective as possible but without the need for ear defenders while cooking

I'm looking at this Luxair hood and the stats are here:

https://luxairhoods.com/image/catalog/PDF/Cooker Hoods/Wall Hoods/STD/LA-STD Technical Info 2.pdf

They put a smaller motor in the 60-90cm hoods, and a larger one in the 100-110cm hoods. The larger motor pulls a heck of a lot more air, but is quieter. All the stats are in the link. But for example, the best comparative is speed 3 on the smaller vs speed 2 on the larger.

Small motor = 680m³/hr. 61dB.
Large motor = 700m³/hr. 52dB.

I have been speaking to Luxair about other stuff and tbh I'm not convinced by all of their answers and specs. Which is why I thought I'd check with you guys whether this seems plausible or illogical.

Any thoughts?

Cheers

 

[Burnerman]

I would imagine the fan sizes are different, hence the noise reduction....the faster the fan, the greater the noise?
John

 

[endecotp]

Larger diameter fans are much quieter than small diameter fans for the same extraction rate.

Small motor = 680m³/hr. 61dB.
Large motor = 700m³/hr. 52dB.

... which is what you have there; almost the same extraction rate, larger is quieter.

 

[StephenOak]

Larger diameter fans are much quieter than small diameter fans for the same extraction rate.

Because the area swept by the fan (roughly corresponds to the volume moved per minute) varies with the square of the radius. A 5" diameter fan has half the area of a 7" one and so has to rotate twice as fast to shift air at the same rate.

Air resistance, and so roughly noise, also varies with the square of the linear speed. So a slower fan will make less noise.

Also, remember that decibels are a logarithmic scale, so a reduction of 10 (61-52=9, which is close) means the sound amplitude is reduced by 2/3.

 

[dontbelieveawordofit]

bigger motors shift more air =more noise.
also larger ducting makes more noise.
especially aluminium.

 

[StephenOak]

bigger motors shift more air =more noise.

Total nonsense.

Corcorde used RR Olympus engines, 1212mm in diameter, max. thrust (dry) 134.9 kN
Boeing 777 used RR Trent 800 engines, 2800mm in diameter, max. thrust 340.6-413.4 kN

Which of those is noisier?

A larger motor, with a larger fan, turning at the same speed will be noisier.
A larger motor, with a larger fan, turning at a slower speed can shift more air and be quieter.

 

[dontbelieveawordofit]

stop being a tw&t. he’s talking about kitchen extractors not jet engines.

 

[StephenOak]

Well you should stop posting nonsense. You made a blanket statement covering all motors in all conditions, so it applies to jet engines, and what you said is as wrong about kitchen extractors as it is about jet engines.

The noise level depends on a lot of things not just the motor size, look

Small motor = 680m³/hr. 61dB.
Large motor = 700m³/hr. 52dB.

bigger motor less noise.

 

[dontbelieveawordofit]

to be honest matey a motor in the context of the thread would normally mean that the guy is looking for an electric one.
I wouldn’t even expect someone to turn up quoting facts and figures about jet aircraft engines.
of course if you want to continue being a tw&t go right ahead.

 

[dontbelieveawordofit]

Well you should stop posting nonsense. You made a blanket statement covering all motors in all conditions, so it applies to jet engines, and what you said is as wrong about kitchen extractors as it is about jet engines.

The noise level depends on a lot of things not just the motor size, look

bigger motor less noise.

wrong . I fit them all the time. it’s my job. in kitchens and bathrooms.
not trawling wikipedia for statistics on the concorde engine.

 

[dontbelieveawordofit]

Hi

I'm looking at getting a new cooker hood. Like most people I guess, I want it to be as effective as possible but without the need for ear defenders while cooking

I'm looking at this Luxair hood and the stats are here:

https://luxairhoods.com/image/catalog/PDF/Cooker Hoods/Wall Hoods/STD/LA-STD Technical Info 2.pdf

They put a smaller motor in the 60-90cm hoods, and a larger one in the 100-110cm hoods. The larger motor pulls a heck of a lot more air, but is quieter. All the stats are in the link. But for example, the best comparative is speed 3 on the smaller vs speed 2 on the larger.

Small motor = 680m³/hr. 61dB.
Large motor = 700m³/hr. 52dB.

I have been speaking to Luxair about other stuff and tbh I'm not convinced by all of their answers and specs. Which is why I thought I'd check with you guys whether this seems plausible or illogical.

Any thoughts?

Cheers

tell you what , buy both and come back with REAL figures.
the large motor may well be quieter , but the larger ducting will make it a whole lot noisier.

 

[StephenOak]

So you wrote nonsense and when that is pointed out rather than admitting it you are abusive and did you heels in. Says a lot about you.

I fit them all the time.

So, at best, what you can say is that for the extractors you fit ones with more powerful motors are normally noisier.

What you can't comment on with any reliability is all extractor fans in the world, but that is what you did.

And if you are such an expert, why are you not commenting on the particular ones the OP asked about? Maybe because you know nothing about them.

 

[endecotp]

benny, please. Generally people only use larger motors/fans/ducting because they have to to get the higher rate they need. If you don’t do that, but just increase the size while keeping the rate the same, then the larger thing will be quieter. It’s just that no-one ever installs large fans/ducts when they could get away with a smaller one because £££. If you really really need as quiet as possible and don’t care about cost then undoubtedly larger diameter fans (running at low rpm) and larger ducts will be quieter.

 

[Tetrarch]

We've had an 80cm Elica Galaxy for about 5 years now. It runs at 64db and it is noisy.

However....

Due to (what turned out to be) a PCB failure we were without the extractor for nearly two months. Now it is back in service (after a 34 quid fix) the difference it makes to the air quality and humidity in a busy kitchen is enormous. We rarely have it on its highest settings, mostly 1 or 2 out of a maximum of 4 does the job.

There is a trade-off between noise and efficiency. In my opinion the latter outweighs the former

Regards

Tet

 

[dontbelieveawordofit]

Says a lot about you.

it’s not about me though is it.