Quietest server: Lenovo's ST50 V3 declares 20.3 dBA at idle

Which server is the quietest?

Lenovo's ThinkSystem ST50 V3 is the quietest server we found, declared at 20.3 dBA at the bystander position when idling in its typical build. HPE's ML30 Gen11 and ML110 Gen11 follow at 22 dBA.

Idle bystander sound pressure (LpAm) for current US tower servers, lowest declared build:

The top five sit within 3.7 dB of each other. Every maker tested a different build, Dell at 25 °C, HPE at 23 °C and Lenovo at 23 °C plus or minus 2 for the ST50 V3, so a one or two decibel gap is closer to a tie than a win.

How do server makers declare noise?

Dell, Lenovo and HPE measure under ISO 7779 and declare under ISO 9296, which gives two figures per mode: sound pressure at the bystander positions (LpAm) and sound power in bels.

Bystander sound pressure

LpAm is the average A-weighted level at the bystander positions around the server, about where a coworker would stand. HPE rounds it "to the nearest 1 dB," Dell prints whole decibels, and Lenovo often gives one decimal place. It is the figure this page ranks across brands.

Dell is the only maker that says where the box sat: towers "on a standard table, 75 cm above a reflective floor," and rack servers and the T560 "in a 24U rack enclosure, 25 cm above a reflective floor."

Sound power and the Kv adder

Sound power is the total noise a server radiates, given in bels, where HPE notes that "1 B = 10 dB." Dell and HPE both declare the mean level, LWA,m, with a 0.4 B verification adder, Kv, listed next to it.

HPE explains that LWA,c, "formerly called LWAd," is LWA,m plus Kv. Lenovo labels its figures LWAd and prints no Kv, so we keep Lenovo's sound power in a separate group. The explainer on sound power and pressure covers why the two never rank together.

Which server has the lowest sound power?

HPE's MicroServer Gen11 has the lowest sound power among the Dell and HPE servers, 3.4 B at idle; in Lenovo's separate LWAd group, the ST50 V3 is lowest at 3.4 Bel.

Idle declared mean sound power (LWA,m), Dell and HPE, lowest build:

Two details need care. HPE's MicroServer table heads the row LWAd, while the paragraph above it calls the same values LWA,m and lists Kv separately; we read them as LWA,m. Dell's T360 prints its lowest idle sound power, 3.5 B, for the Feature Rich Max. Storage build, whose bystander level is 28 dB, against 3.6 B and 24 dB for the Quietest Config.

Lenovo's LWAd group at idle, typical builds: ST50 V3 3.4 Bel, ST45 V3 3.5 Bel, ST250 V3 4.6 Bel, SR250 V3 4.9 Bel.

How loud do these servers get under load?

Under load the order holds near the top: Lenovo's ST50 V3 stays at 20.3 dBA at half its CPU TDP, HPE's ML30 Gen11 stays at 22 dBA, and Dell's T360 rises to 27 dB.

Makers define "operating" in different ways, so only like loads compare well. Three makers use half the CPU's thermal design power for at least one model:

• Lenovo ST50 V3, Operating 1: 20.3 dBA typical
• HPE ML110 Gen11, Entry builds: 24 dBA
• Dell T360, Quietest Config: 27 dB
• Dell T160, Economy: 28 dB

At full TDP the ST50 V3 reaches 35.1 dBA. Lenovo runs the ST250 V3 and SR250 V3 at 70% for Operating 1, and gives no load at all for the ST45 V3's 40 dBA. HPE's ML30, MicroServer and DL20 sheets print the same LpAm for idle and operating without naming a load.

Dell adds a hotter test. At 35 °C under maximum loading, the T160 Economy build reaches 41 dB and the T360 Quietest Config 61 dB.

Why does configuration change a server's noise?

Configuration changes a server's noise because fans speed up to cool hotter parts, and every maker here says its figures hold only for the build it tested.

Dell's T560 guide lists the main drivers: ambient temperature above 25 °C, higher TDP processors, NVMe drives that "pre-heat down-stream components," the thermal profile chosen in BIOS or iDRAC, and PCIe cards such as a 25 Gb NIC or a GPU of 75 W or more.

The tables show it. Dell's T360 goes from 24 dB idle in its quietest build to 37 dB in the Volume Plus build, which adds a BOSS boot card, and 41 dB with a GPU. Lenovo's ST50 V3 maximum build, with three drives, an SSD, a RAID card and a NIC, idles at 27.6 dBA.

HPE's ML30 and MicroServer sheets add a software catch: HPE's AMS tools are "Required" in the operating system so iLO can read drive temperatures, "otherwise may experience acoustic noise impact."

What is the quietest rack server?

HPE's ProLiant DL20 Gen11 is the quietest small rack server we found, at 27 dBA idle and operating in three of its four builds and 28 dBA in Entry.

The other current 1U servers, lowest idle build:

• Dell PowerEdge R260: 30 dB (Economy, Volume, Volume with BOSS)
• Dell PowerEdge R360: 35 dB (Quietest)
• Lenovo ThinkSystem SR250 V3: 35.7 dBA (Typical)

Dell measured both of its 1U servers in a 24U rack enclosure 25 cm off the floor, where its towers sat on a table, so placement differs from the tower list. Even the DL20 sits 6.7 dB above the ST50 V3, and Dell describes the R260 as fit for an office only "with typical loading condition."

Is a tower server quieter than a NAS or a mini PC?

The figures cannot settle it, because NAS and mini PC makers use their own distances and setups rather than ISO 9296 bystander positions, so their decibels and a server's LpAm do not line up.

A server earns its place with ECC memory, remote management and room for more drives. If you only need file storage or a few containers, our quietest NAS guide and quietest mini PC guide cover smaller boxes, and the quietest desktop PCs cover workstation towers.

For where a server sits in a working room, the quiet home office page has the wider picture.

Do Supermicro tower servers print decibels?

No, the Supermicro tower pages we read give no decibel figure. The SYS-531A-IL page describes a "12cm PWM quiet exhaust fan," and the SYS-531R-I a "9cm PWM quiet exhaust fan," with no number behind either.

We also checked the SYS-551A-T, SYS-532AW-C and SYS-541A-TR pages and found no acoustic data on any of them, so no Supermicro model could be ranked.